For the phylum Cnidaria question, the correct answer is "They coordinate movements
through a noncentralized nerve net." Cnidarians, such as jellyfish, corals, and sea
anemones, have a simple nervous system known as a nerve net that allows them to
coordinate movements and respond to environmental stimuli.
For the question on the most ancient branch point in animal phylogeny, the correct answer is
"true tissues and no tissues." The earliest major split in the animal kingdom is between the
Parazoa, which lack true tissues (e.g., sponges), and the Eumetazoa, which have true
tissues.
For the fill-in-the-blank question, the correct answer is "cnidocytes." Anemones and jellyfish
use cnidocytes, specialized cells that contain harpoon-like structures called nematocysts, to
immobilize prey with venom.
. Diploid-dominant life cycles in animals
Animals are diploid-dominant, meaning their somatic (body) cells are diploid and only the
gametes (sperm and eggs) are haploid. Meiosis is used to produce these haploid gametes,
and mitosis is used for growth and repair of diploid cells.
Other options don't apply because they don't accurately describe the typical life cycle stages
of animals.
. Extracellular matrix of animals and structural support in plants
Chloroplasts and central vacuoles: While central vacuoles do contribute to cell turgidity and
can aid in plant structure, and chloroplasts are important for photosynthesis, they are not
primarily responsible for structural support.
Stomata, Guard Cells, and Mesophyll Cells: These are involved in gas exchange and
photosynthesis in plants, not structural support.
Xylem and Phloem: Xylem does play a role in structural support as it forms part of the woody
tissue in plants, but the primary reason plants can stand tall is due to the rigidity provided by
cell walls and turgor pressure.
. Formation of the coelom in Eucoelomates
Mesenteries prevent blood flow to the area: Mesenteries are membranes that attach organs
to the body wall, and their primary function is not related to the formation of the coelom.
Invagination of the blastopore as the blind gut forms: Invagination of the blastopore leads to
the development of the gut, but this process is not directly related to the formation of the
coelom in the context of this question.
Gastrulation of the blastula: While gastrulation is a crucial step in the development of
embryonic layers, the coelom specifically forms later in development, often through the
process of mesodermal differentiation and not just gastrulation alone.
25. Common ancestor of animals
Mesophyll cells: These are plant cells found in leaves, involved in photosynthesis. Plants are
not particularly close relatives to animals in the tree of life.
Plant cells: Similar to mesophyll cells, plant cells are part of a different kingdom and are not
the closest relatives to animals.
Bacterial cells: Bacteria are far more distantly related to animals, belonging to an entirely
different domain of life (Prokaryota).
Fungal cells are considered the closest among these options because both fungi and
animals belong to the Eukaryota domain, and they share a more recent common ancestor
compared to plants or bacteria.
26. Adaptations for tetrapods on land
Amniotic Eggs and Double jaws: Amniotic eggs were an important development for
land-dwelling vertebrates, but the double jaw is not a recognized adaptation in the transition
to land.
Wings and Exoskeletons: Wings evolved much later in the history of life and are specific to
birds and some insects, not early tetrapods. Exoskeletons are characteristic of invertebrates,
not vertebrate tetrapods.
Limbs & Eyes: Eyes were already present in aquatic ancestors of tetrapods. While the
development of limbs was crucial, eyes did not evolve as a new feature during the transition
to land.
27. Three clades of mammals
Rodentia, Carnivora, Marsupials: Rodentia and Carnivora are orders within the class
Mammalia, specifically within the placental group, not separate clades representing major
divisions of mammals.
Monotremes, Marsupials, Cetaceans: Cetaceans (whales, dolphins) are a group within the
placental mammals and not a separate major clade of Mammalia.
Placentals, Marsupials, Cetaceans: As mentioned, cetaceans are part of the placental group,
not a distinct major clade of mammals.
The best answer is "All of these factors contributed to the Pleistocene die-offs". While the
arrival of humans and their impact through hunting and habitat alteration were significant
factors, climate change and changes in vegetative communities also played crucial roles in
the declines of large mammal species richness after the Pleistocene. This period was
marked by significant climatic fluctuations and habitat changes that, along with human
activities, contributed to the extinction events.
Climate change and changes in vegetative communities: These environmental changes
affected the availability of food and habitats for large mammals.
Natural background extinction rate: While it represents the standard rate of extinction, the
Pleistocene extinctions were more rapid and extensive, suggesting additional factors at play.
Arrival of humans and predation pressure from humans: This had a major impact, especially
through overhunting and habitat destruction, but it was one of several factors.
The correct answer is USA. The Queen Conch (Strombus gigas) is primarily found in the
Caribbean Sea and the Gulf of Mexico, including the waters off the coast of Florida, USA.
India, Saudi Arabia, Australia: These countries do not have the typical habitats where Queen
Conch are found, as they are native to the Caribbean region and not the Indian Ocean, Red
Sea, or waters around Australia.
The correct answer is the most advanced among molluscs. Cephalopods, like octopuses,
squids, and cuttlefish, have highly complex nervous systems, often considered the most
advanced among molluscs.
Primitive and very little advancement since that of cnidarians: This is incorrect because
cephalopods have a much more developed nervous system than cnidarians, which mostly
have a simple nerve net.
A nerve net with a single large eye to detect motion and light: This does not accurately
describe cephalopods, as they have a centralized brain and sophisticated eyes, far beyond a
simple nerve net structure.
None of these choices are correct: This option is incorrect because the statement "the most
advanced among molluscs" accurately describes the cephalopod nervous system.
Vascular or Circulatory tissue because elephantiasis is primarily caused by blockage in the
lymphatic system, which is part of the broader circulatory system in the body. This blockage
leads to the severe swelling and thickening of the skin and tissues, commonly associated
with the disease.
Nervous Systems and Digestive Systems are not directly involved in the pathogenesis of
elephantiasis.
Epidermis or Integumentary Systems might be involved initially as the entry point for the
parasites, but the primary impact and symptomatology of elephantiasis are due to the
obstruction of lymphatic vessels, affecting the circulatory system's function.
The correct answer is Psuedocoelom. Nematodes (roundworms) are unique among animal
phyla because they have a pseudocoelom, a fluid-filled body cavity that is only partially lined
with mesoderm tissue, making it simpler than a true coelom.
Diploblastic Coelom: Incorrect, as nematodes are not diploblastic (they are triploblastic) and
do not have a true coelom.
Smooth Cuticle: While nematodes have a smooth cuticle, it is not unique among animal
phyla and does not describe their body cavity.
Coelom: Nematodes do not have a true coelom but a pseudocoelom.
The correct answer is Eyespots. Turbellarian flatworms, like planarians, have simple
light-sensitive organs called eyespots that can detect changes in light intensity, helping them
navigate their environment.
Ganglia: Incorrect, as ganglia are clusters of nerve cells, not light-sensitive organs.
Auricles: In some flatworms, auricles are sensory structures on the head, used for chemical
sensing, not for light detection.
Statocysts: These are organs used for balance, not for light sensitivity.
34. Planarian feeding mechanism
The correct answer is scraping and sucking food particles into the GVC via a midventral
proboscis. Planarians feed by extending a pharynx (proboscis) from their ventral surface to
scrape and ingest food particles, which are then processed in their gastrovascular cavity.
Engulfing food particles through an anterior mouth and excreting waste via an anus:
Planarians do not have a separate anus; they expel waste through the same opening they
eat from.
Attaching with a sucker and extracting blood via a mouth with triangular teeth: This describes
a parasitic feeding mechanism, which is not typical for non-parasitic planarians.
Sucking nutrients in from the environment and filtering through its flame cell system: Flame
cells are involved in excretion and osmoregulation, not feeding
35. Presence of a coelom in phyla
Annelids: This phylum includes earthworms, which have a true coelom, making this choice
incorrect.
Mollusca: Mollusks, such as snails, clams, and squids, have a coelom, so this choice is also
incorrect.
Chordata: Chordates, which include all vertebrates, have a coelom, thus this choice is
incorrect.
Platyhelminthes, or flatworms, lack a coelom, making them the correct answer as they are
acoelomate organisms.
36. Oldest fossil sponges and silica spicules
Makes Sponges paraphyletic: Paraphyletic refers to a group that includes some but not all
descendants of a common ancestor. Finding silica spicules doesn’t make sponges
paraphyletic; it provides information about their evolutionary history.
Is not phylogenetically informative: This is incorrect because the discovery of silica spicules
in the oldest sponges is indeed phylogenetically informative; it helps to trace the evolutionary
lineage and characteristics of early sponges.
Does not support this tree: Without specific context about "this tree," it’s hard to say it
doesn’t support it. However, if "this tree" refers to the accepted evolutionary position of
sponges, then finding silica spicules would likely support, not contradict, the phylogenetic
tree.
Sea turtles can eat sponges regardless of the spicule type because they have thick skin
covered in scales, which protects even their mouths and tongues from the sharp spicules.
This adaptation allows them to consume sponges without injury from the hard, often
siliceous spicules that sponges contain.
For the fill-in-the-blank question, the answer is external fertilization. In sponges, fertilization
occurs outside the individual’s body, where the sperm is released into the water and enters
another sponge to fertilize the egg.
Regarding reptile global distribution, reptiles are least successful in terms of species
richness in the Polar regions. Reptiles are ectothermic (cold-blooded) and rely on external
heat sources to regulate their body temperature, making it difficult for them to survive in the
cold, harsh conditions of polar environments.
Tropical regions: Incorrect, as these areas have the highest reptile diversity and species
richness.
Islands and Archipelagos: Many islands, especially in tropical regions, have a high diversity
of reptiles.
Temperate Regions: While temperate regions have fewer reptile species than tropical areas,
they are still more hospitable to reptiles than polar regions.
The correct answer is None of the chordate synapomorphic traits are missing. Ascidian sea
squirt tadpoles possess all the key chordate features during their larval stage, including a
notochord, a dorsal nerve cord, pharyngeal slits, and a post-anal tail. These features are
characteristic of chordates, and while the adult form of sea squirts looks quite different, the
larval stage clearly exhibits these chordate traits.
If sponges have homeotic genes but no Hox genes, this finding would confirm the identity of
sponges as basal animals. Homeotic genes without Hox genes suggest an early stage in the
evolution of regulatory genes controlling body plan development. This supports the idea that
sponges are among the earliest diverging animal lineages, lacking the complex body
segmentation and axis development seen in more derived animals.
Strengthen ties to Eumetazoa: Incorrect, as Eumetazoa typically have both homeotic and
Hox genes, indicating more complex body plans.
Extinct sponges as last common ancestor of animals and fungi: This is misleading; while
sponges are ancient, they are not directly related to the animal-fungi divergence.
Sponges no longer classified as animals: Incorrect, as the presence of homeotic genes still
aligns with the animal kingdom, and classification as animals doesn't solely depend on Hox
genes.
The correct answer is All of these are used by at least a few species of caterpillar.
Caterpillars employ various strategies to avoid predation, including aposematic coloration to
warn predators of toxicity, camouflage to blend in with their surroundings, and venomous
spines or hairs to deter attackers. These adaptations are seen across different species,
showcasing the diverse defensive mechanisms evolved by caterpillars to survive predation
threats.
Organisms like flatworms, with a solid body and no fluid-filled cavity within the mesoderm,
are Acoelomates. This term refers to the lack of a true coelom (body cavity) within the
mesoderm.
For the question about data misplacing animals in relation to evolutionary relationships, the
correct answer is morphological : molecular. Morphological data, based on physical form and
structure, can sometimes lead to misplacement of animals due to convergent evolution,
where unrelated species evolve similar traits. Molecular data, however, often provides a
more accurate evolutionary relationship because it is based on genetic information, which is
less likely to be influenced by environmental factors and convergent evolution.
The three types of germ layers are Endoderm, Ectoderm, and Mesoderm. These are the
fundamental layers formed during early embryonic development in animals, leading to the
formation of different tissues and organs:
The Endoderm is the innermost layer that forms the lining of the digestive tract and other
internal organs.
The Ectoderm is the outermost layer that forms structures such as the skin and nervous
system.
The Mesoderm is the middle layer that forms the muscles, bones, and circulatory system.
The correct answer is Diploid-dominant. Animals typically have diploid-dominant life cycles,
meaning the primary body form is diploid, and meiosis results in haploid gametes for
reproduction, with mitosis occurring for growth and repair in the diploid phase.
Hox genes determine the body plan along the Anterior-Posterior axis, meaning they control
the development from the head (anterior) to the tail (posterior) of the organism.
The branch of biology that studies animals is Zoology. This field encompasses various
aspects of animal life, including behavior, physiology, genetics, ecology, and evolution.
The structural component that holds animal cells together is Collagen. Collagen is a protein
that forms a key part of the extracellular matrix and provides structural support, helping to
hold cells and tissues together.
As previously mentioned, it is common for morphological : molecular data to misplace
animals in close relation to other species. Morphological data based on physical and
structural characteristics can sometimes lead to incorrect evolutionary assumptions, which
molecular data, based on DNA and genetic analysis, often corrects by revealing more
accurate evolutionary relationships.
Animals with three well-defined germ layers (ectoderm, mesoderm, and endoderm) and that
have one solid mass of tissue rather than tissues and organs nestled inside a body cavity
are acoelomate and triploblastic. Acoelomates do not have a fluid-filled body cavity (coelom)
between the gut and the body wall, and triploblastic means having three germ layers.
The members of the clade Anthozoa (Corals and Anemones) in the phylum Cnidaria exist
only as polyps. Unlike some other cnidarians that exhibit both polyp and medusa stages,
anthozoans remain in the polyp form throughout their lifecycle.
According to the evidence collected so far, the animal kingdom is Monophyletic, meaning all
animals are believed to have descended from a common ancestor, and this group includes
all descendants of that ancestor.
In members of the phylum Cnidaria, the Gastrovascular Cavity functions as both a mouth
and an anus. This cavity is where digestion takes place, and the single opening serves to
both ingest food and expel waste
The Hydra has only one opening into its Gastrovascular Cavity (GVC), and therefore the gut
is Blind. This means the organism has a single opening that serves as both mouth and anus,
with no separate exit for waste.
Gastrovascular Cavity (GVC); Complete: Incorrect because a complete digestive system has
two openings, one for ingestion (mouth) and one for waste excretion (anus).
Tube-within-a-tube; Blind: The term "tube-within-a-tube" refers to a body plan with a
separate mouth and anus, which does not apply to Hydra.
Sac-like Gut; Compartmentalized: Hydra does not have a compartmentalized gut; it has a
simple, singular digestive chamber.
Anemones and jellyfish use Cnidocytes to shoot out harpoon-like projectiles with venomous
spines to immobilize prey.
Radiocytes: Not a real term related to the cnidarian stinging mechanism.
Choanocytes: These are cells found in sponges, not cnidarians, used for feeding and water
flow.
Pinocytes: Involved in cellular drinking or pinocytosis, not in delivering stings or capturing
prey.
It is common for morphological : molecular data to misplace animals in close relation to other
species. Morphological data can lead to misclassification due to convergent evolution, where
different species evolve similar traits independently, while molecular data often provides a
more accurate evolutionary relationship based on genetic information.
Molecular : fossil record: Incorrect as molecular data generally provides more precise
phylogenetic placements than the fossil record.
Molecular : morphological: This reversal is incorrect because it is the morphological data that
can be misleading, not the molecular.
Fossil record : morphological: The fossil record can provide important context for
morphological analysis, but it is the molecular data that often clarifies the evolutionary
relationships when morphology is ambiguous.
Sponges lack true tissues because their cells can reaggregate and display a high degree of
cellular autonomy, unlike organisms with more complex, organized tissue structures.
The tapeworms are a monophyletic group in the phylum Platyhelminthes (flatworms).
Tapeworms belong to this phylum, characterized by their flat, ribbon-like bodies.
The cocoon, which contains the fertilized eggs in the earthworm, is produced by the
Clitellum. This is a thickened, glandular section of the body wall in earthworms and some
other annelids, which secretes a mucous sheath used to form the cocoon for eggs.
61.Most Bivalvia are filter feeders, using their muscular siphons to create water currents that
bring in food particles from the surrounding water.
Bivalvia as filter feeders:
Bivalvia are known for their filter-feeding mechanism; they do not employ other feeding
strategies like predation or scavenging typically.
62.When humans consume the eggs or proglottids of the Pork Tapeworm, the larvae can
migrate to the Brain and form cysts, leading to a condition known as neurocysticercosis,
which can be painful and potentially fatal if untreated.
The Pancreas, Liver, and Bladder are not the primary locations where cysts form in the case
of cysticercosis caused by Pork Tapeworm; it's primarily the brain where the most serious
effects occur.
63.The hard cuticle of arthropods is composed of Mineralized chitin and must be shed during
the process of molting (ecdysis) to allow for growth
Collagen and calcified ossicles are not typical components of arthropod cuticles.
Segmented keratin and Lignified cellulose are not materials found in the arthropod cuticle,
which is mainly made of chitin
The notochord and hollow nerve cord are surrounded by the Ectoderm germ layer, which
gives rise to the central nervous system, including the brain and spinal cord, in vertebrates.
Epidermis is incorrect because it's the outermost layer of the skin, not related to the
development of the central nervous system like the ectoderm.
65.The phylum that contains the polychaetes, marine worms which often filter feed, is
Annelida. Polychaetes are a diverse group of annelid worms known for their segmented
bodies and often elaborate bristles.
Platyhelminthes and Nematoda are incorrect because these phyla contain flatworms and
roundworms, respectively, not polychaetes.
Mollusca is also incorrect because this phylum includes snails, clams, and other mollusks,
not segmented worms like polychaetes.
The phylum with a clitellum that produces cocoons is Annelida. The clitellum is a feature of
earthworms and some other annelids, used in reproduction to create cocoons for their eggs.
The phylum with a ladder-like nervous system is Platyhelminthes (flatworms). This nervous
system structure consists of two longitudinal nerve cords connected by transverse links,
resembling a ladder.
Nematoda and Annelida do not have a ladder-like nervous system typical of flatworms.
For the third question regarding the sea squirt (Urochordate) and its method of obtaining
food, the correct comparison would be with a Sponge. Like sponges, sea squirts are filter
feeders that draw water into their bodies, filter out food particles, and then expel the water.
They use their siphons to create a current that brings water and food particles into their
bodies, similar to how sponges pull water through their porous structures to filter out
nutrients.
Here's why the other options are not correct:
Bivalve: While bivalves are also filter feeders, they have a different anatomical structure and
method of filtering compared to sea squirts. Bivalves use gills for filtering, not siphons.
Annelid fan worm: These worms use their crowns to catch particles from the water, which is
a different mechanism compared to the internal filtering system of sea squirts.
Gastropod: Gastropods generally use a radula to graze or capture food, which is quite
different from the filter-feeding method of sea squirts.
Tunicate larvae have rudimentary eyespots, but the adult sea squirts have No eyes. They
lose these sensory structures as they metamorphose into sessile adults.
Adult sea squirts do not have eyes; they lose their sensory organs as they transition to a
sessile lifestyle.
In terms of food capture, the sponge cell most similar to the cnidocyte of a cnidarian is the
Choanocyte. Choanocytes create a current to draw water into the sponge, trapping food
particles, somewhat analogous to how cnidocytes capture prey for cnidarians, although the
mechanisms are quite different.Epidermal Cell, Amoebocyte, and Mesohyl in sponges are
not involved in food capture in the same way as cnidocytes in cnidarians. Amoebocytes are
involved in digestion and transport within sponges, while mesohyl acts as a gelatinous matrix
within the sponge, and epidermal cells form the sponge's outer layer.
The last common ancestor of all animals was probably a Heterotrophic Protist. This ancestor
would have been an organism that consumed organic material for energy, similar to how
animals feed, rather than producing its own food through photosynthesis like plants or algae.
The trait that is not a main feature of all animals is Haploid-dominant life cycle, with larva.
Animals generally have a diploid-dominant life cycle, where the main stage of life is diploid
and meiosis produces haploid gametes for reproduction. The haploid stage is not the
dominant phase in the life cycle of most animals
The Opisthokont clade is characterized by the presence of a single posterior flagellum on
swimming cells, such as sperm cells or the entire organism in the case of the flagellate stage
of choanoflagellates. This clade includes both the fungi and the animals, as well as the
choanoflagellates, which are considered the closest living relatives of animals. The defining
characteristics of opisthokonts are shared with flagellated heterotrophic protists, suggesting
a close evolutionary relationship.
Let's break down why the other options are less likely to be the sister taxa to Opisthokonts:
A. Non-Vascular Plants: These are part of the Plant Kingdom and are autotrophic, meaning
they produce their own food through photosynthesis. They have a very different mode of
nutrition and cell structure compared to the mostly heterotrophic opisthokonts, which include
organisms that primarily consume organic material for energy.
B. Gram-negative Bacteria: These organisms are prokaryotes, lacking a defined nucleus and
other membrane-bound organelles present in the cells of opisthokonts, which are
eukaryotes. The structural and genetic differences are significant, making them a very
distant relation to the eukaryotic opisthokonts.
C. Colonial Photosynthetic Protists: These organisms, which include algae, perform
photosynthesis and are autotrophic. Their lifestyle and cellular organization are quite
different from the heterotrophic lifestyle of opisthokonts. Furthermore, their photosynthetic
nature distinguishes them significantly from the mostly non-photosynthetic opisthokonts.
D. Flagellated Heterotrophic Protists: These organisms share several characteristics with
opisthokonts, such as heterotrophy (relying on external organic material for energy) and the
presence of flagella. These shared traits suggest a closer evolutionary relationship with the
opisthokonts, making it more likely that they would be considered a sister group in a
phylogenetic sense. The flagellated condition and mode of nutrition make this group a more
plausible sister taxa to the opisthokonts, which also evolved from flagellated, heterotrophic
ancestors.
The correct answer is D. All of these traits make animals monophyletic. Here's why each of
the individual traits is evidence for the monophyly of animals, and the other options are not
standalone evidence:
A. Only animals have an embryonic blastula: The blastula stage is a characteristic feature of
animal development. This hollow ball of cells occurs after fertilization and is a key stage
before differentiation into more complex structures.
B. Only animals have Hox genes: Hox genes are a group of related genes that control the
body plan of an embryo along the head-tail axis. After the embryonic segments have formed,
Hox proteins determine the type of segment structures (e.g., legs, antennae, and wings in
fruit flies) that will form on a given segment. Hox genes are present across various animal
taxa, but not outside the animal kingdom.
C. Only animals contain collagen: Collagen is the main structural protein in the extracellular
matrix of animals' connective tissues. It is abundant in mammals, comprising a significant
part of skin, bones, tendons, and other structures, and it is not found in plants or fungi.
Each of these traits is unique to the animal kingdom and supports the idea that animals are
derived from a common ancestor, which is the definition of a monophyletic group. When all
these traits are considered together, they provide strong evidence supporting the
monophyletic status of animals.
Based on homology and the characteristics shared among diverse animal groups, the most
recent common ancestor (MRCA) of all animals most likely had A. external fertilization. This
mode of reproduction is found in many different animal groups, particularly in aquatic
environments where the majority of animal phyla originated. External fertilization is a
primitive trait where gametes are released into the water and fertilization occurs outside the
body, which is common in many basal animal groups.
Here’s why the other options are less likely:
B. Hermaphroditism: While hermaphroditism is present in many animal lineages, it's not as
fundamental a trait as external fertilization and tends to be more specific to certain groups
rather than a characteristic of the earliest common ancestor.
C. Internal fertilization: This is more derived and generally associated with terrestrial life or
specific adaptations in aquatic environments, suggesting that it evolved later than external
fertilization.
D. Alternation of Generations: This is a reproductive cycle where an organism alternates
between haploid and diploid forms. It's more commonly associated with plants and certain
algae and is not a widespread trait among the majority of animal phyla.
The cross-section labeled as B represents a pseudocoelomate, characterized by a body
cavity that is not entirely lined with mesoderm. This feature is indicative of the Nematoda
phylum, where the pseudocoel serves as a fluid-filled cavity that holds the internal organs
and is only partially lined with mesodermal tissue.
Cephalization is the presence of a head or head-like region where structures for feeding,
sensing the environment, and processing information are concentrated. Of the animals
shown, if there is one with a distinct head region where sensory organs are clustered, that
would be the cephalized animal.
Typically, slugs like the one in picture D have a head with sensory tentacles and eyespots,
and a mouth, which indicates cephalization. Starfish and sea squirts do not have this
concentration of sensory structures in a head region; they have a more radially symmetrical
or less centralized body plan. So, among the options given in the image, the slug (D) is the
cephalized animal.
Based on the image description, you're looking to compare the surface area of choanocytes
(red cells) in different sponge types. Choanocytes, also known as "collar cells," line the inner
chambers of sponges and are responsible for generating water flow and filtering food
particles from the water.
In such a comparison:
A simple tube with choanocytes would have the least surface area.
A more complex folded tube would have a greater surface area due to the folds increasing
the lining's extent.
The most complex structure with multiple infoldings and chambers would provide the
greatest surface area for choanocytes.
Without seeing the image, I would infer that the sponge with the most complex infoldings
(likely represented by the image with the most red cells) would have the greatest surface
area of choanocytes, thus being the most efficient at feeding and water filtration. If one of the
images shows a structure with multiple branches or infoldings lined with red cells, that would
likely be the correct answer, often resembling the structure of a more complex sponge type
like a leuconoid sponge.
Sponges are said to lack true tissues primarily because E. their cells can change from one
type to another. This cellular plasticity allows sponge cells to differentiate and change
functions, which is a characteristic not found in organisms with true tissues where cells are
generally fixed in their roles.
While sponges do have different cell types, including choanocytes for feeding and porocytes
for water flow, these cells are not organized into true tissues due to their ability to transform
from one type to another, a phenomenon known as cellular totipotency. This trait sets
sponges apart from other animal groups that have specialized, non-interchangeable tissues
and cells.
Understood, the moon jelly (Aurelia sp.) has a D. dioecious medusa stage. This means that
the species has distinct male and female medusae that participate in sexual reproduction,
contrasting with hermaphroditic species where individuals may have both male and female
reproductive organs.
The life cycle of Pelagia differs from that of Aurelia in that Pelagia has no B. Polyp stage.
While Aurelia undergoes a typical cnidarian life cycle with both polyp and medusa stages,
Pelagia, commonly known as the mauve stinger, lacks the sessile polyp stage and directly
develops from the larval stage into the medusa form.
Here's why the other answers are not correct:
A. The foot - While changes in the foot are evident, this answer choice is incomplete
because it doesn't account for other changes.
B. The body form - This choice, like A, is too narrow because it considers only one aspect of
the diversity shown.
C. The radula - The radula is a feeding organ, but it does not account for all the diversity
shown on the tree. While it is lost in bivalves, it's not a change represented across all
groups.
E. (A), (B), and (C) - This choice incorrectly includes the radula as a factor for all mollusk
diversity in the tree, which is not supported by the diagram. Only gastropods and chitons are
shown to have a radula, with bivalves having lost it and cephalopods not being mentioned in
relation to the radula at all.
The correct answer is D (A and B) because:
Changes in the foot are indicated, as seen in the transition from chitons (with a simple foot)
to cephalopods (where the foot is modified into arms).
Changes in body form are also shown, such as the coiled shell in gastropods, the reduction
of the head and loss of the radula in bivalves, and the torsion of the body in gastropods.
Each of these changes involves both the foot and the overall body form, which are crucial in
the diversification of mollusks according to the cladogram. Thus, both A and B are correct,
but C is not included because the changes related to the radula are not consistent across all
groups.
Here's a breakdown of why the other answers are not correct in this context:
A. Chitons - Chitons have a relatively simple and similar foot structure across the group,
which they use for attachment to rocks and surfaces in their marine environment. There isn't
a significant diversity in the arrangement of their foot.
B. Bivalves - The foot of bivalves is also not very diverse. It is typically used for digging or
anchoring into sediment. Bivalves include clams, oysters, and mussels, and their foot
structure does not vary greatly within the group.
C. Gastropods - This group includes snails and slugs, which do show variation in their foot;
however, it is primarily used for locomotion in a similar manner across the group. The
diversity in the foot structure is present but not as extreme as in cephalopods.
D. Cephalopods - This group includes animals like squids, octopuses, and cuttlefish.
Cephalopods have the most diverse foot structures as their foot has evolved into a complex
array of tentacles and arms with various adaptations for locomotion, capturing prey, and
manipulating the environment. This represents a significant evolutionary divergence from the
typical mollusk foot structure.
The diversity (disparity) in cephalopods' foot arrangement is the most extensive among the
options given, which is why D is the correct answer. They have adapted their foot into a
variety of forms for different functions, which is unmatched by the other mollusk classes
listed.
The Mimic Octopus (Thaumoctopus mimicus) is known for its ability to impersonate other
sea creatures. The correct answer to why the Mimic Octopus is "mimicking" the Lionfish and
the Sea Snake is:
B. Both are venomous, and this is an aposematic signal to potential predators.
Here’s why the other answers are not correct:
A. For better camouflage against the reef - Mimicry of the lionfish or sea snake is not
primarily for blending in with the reef but to mimic the appearance of venomous or
dangerous animals.
C. The Octopus is attempting to trick prey items into getting close to it, both sea snakes and
lionfish are non-aggressive feeders - The purpose of mimicry in this case is not to attract
prey but to deter predators. Sea snakes and lionfish may not be characterized as
"non-aggressive" feeders; rather, they are capable of capturing prey efficiently, albeit through
different methods.
D. The Lionfish and Sea Snake are "mimicking" the Octopus not the other way around - This
statement is incorrect because it is the mimic octopus that is known for its ability to mimic
other creatures, not the other way around.
The mimic octopus uses mimicry as a defense mechanism to avoid predation by appearing
as other species that are dangerous or unpalatable. Both the lionfish and certain sea snakes
are known for their venom, and by mimicking these creatures, the octopus is leveraging the
predators' avoidance of these venomous animals to reduce the risk of being eaten itself.
The correct answer to the question is A, which refers to the organism adapted
morphologically as a filter feeder among the annelids shown.
The reason the other options are not correct:
B. This looks like a crab with a worm-like creature on it, which is not demonstrating
filter-feeding morphology.
C. This annelid has a morphology consistent with a burrowing lifestyle, not filter feeding.
D. The worm here appears to have appendages for crawling and perhaps digging rather
than filter feeding.
E. This looks like an earthworm, which is a soil-dwelling creature that feeds on soil and
organic matter, not by filter feeding.
In contrast, organism A shows fan-like structures, which are indicative of a filter feeder.
These structures are used to capture food particles from the water, which is a hallmark of
filter-feeding organisms. This organism is likely a species of feather duster worm or a similar
sedentary polychaete that uses its feathery appendages to filter food from the water column.
The correct answer is B: Vascular or Circulatory tissue.
Elephantiasis is a condition typically caused by filarial worms, which are a type of nematode
that infects the lymphatic system, part of the circulatory system. The worms cause blockage
in the lymphatic system, leading to severe swelling and thickening of the skin.
Similarly, carrot root disease in plants, caused by nematodes, affects the roots which are
part of the plant's vascular system, responsible for the transport of water and nutrients.
Here's why the other answers are not correct:
A. Epidermis or Integumentary system - While the symptoms of elephantiasis include
changes to the skin, the primary infection is not in the epidermis but rather in the lymphatic
vessels which are part of the circulatory system.
C. Nervous System - Nematodes that cause elephantiasis and carrot root disease do not
primarily target the nervous system.
D. Support System - In humans, the support system would refer to the skeletal system, and
in plants, it could refer to structural tissues like xylem and phloem. However, the diseases
mentioned do not primarily target these systems but are related to the circulatory and
vascular tissues.
The correct answer to the question about the homology between arthropods and annelids is
C: Bilateral symmetry.
Here's why the other options are not correct:
A. Spiral cleavage - This is characteristic of a different group within the protostomes called
Spiralia, which includes molluscs and annelids, but not arthropods.
B. Ecdysis - This refers to the process of molting, which is typical of Ecdysozoa (a group that
includes arthropods and nematodes), but not generally associated with annelids.
D. Radial cleavage - This type of cleavage is characteristic of deuterostomes, not
protostomes like arthropods and annelids.
E. Compound eyes - While many arthropods have compound eyes, this is not a feature
shared with annelids.
Bilateral symmetry is a fundamental characteristic of the body plan that is shared by both
annelids and arthropods. It means that the body can be divided into roughly mirror-image
halves along a single plane, which is a common feature in the animal kingdom and a point of
homology for these two phyla.
The answer to the question is indeed A: Homoplasy (from convergent processes).
In evolutionary biology, homoplasy occurs when traits are similar due to convergent
evolution, not because of a shared ancestry. Convergent evolution happens when distinct
lineages independently evolve similar traits as a result of having to adapt to similar
environments or ecological niches.
The cladogram in the image indicates that tracheae are found in both myriapods and
hexapods (a group that includes insects). However, if these traits were homologous, we
would expect to see tracheae in the common ancestor of myriapods, hexapods, and
crustaceans. Since tracheae are not indicated in the common ancestor on the cladogram, it
suggests that tracheae developed independently in myriapods and hexapods after these
lineages diverged. This is an example of convergent evolution, making the tracheae a
homoplastic characteristic.
Here's why the other answers are not correct:
B. Homologous - This would imply that the trait was inherited from a common ancestor,
which is not supported by the tree as tracheae are not shown in the group including
crustaceans.
C. Coevolved - This term usually refers to two or more species influencing each other's
evolution due to close ecological interactions. It doesn't apply to traits within a species or
lineage.
D. A synapomorphy of arthropods - A synapomorphy is a trait shared by a group of
organisms due to inheritance from a common ancestor. If tracheae were a synapomorphy of
arthropods, we would expect all arthropods to have tracheae, but the cladogram does not
show tracheae in crustaceans.
E. Present in chelicerates too - The cladogram does not indicate that chelicerates have
tracheae, so this is not supported by the information provided.
The answer indicated as D: Swimming suggests that the crustacean has the most segments
devoted to swimming. In many crustaceans, like crayfish, there are specialized appendages
used for swimming called swimmerets or pleopods, which are found on the underside of the
abdomen (the tail region). These swimmerets are often numerous and move rhythmically to
propel the crustacean through water, which would align with the answer provided.
While crustaceans do have segments and appendages dedicated to sensory functions,
defense, and walking, the fact that swimming is highlighted as the correct answer indicates
that the diagram probably shows a significant number of segments dedicated to swimming
limbs, which is a distinguishing feature in the morphology of some crustaceans, particularly
those that are adept swimmers.
The notochord is not the same as the spinal cord. In chordates, the notochord is a flexible
rod made out of a material similar to cartilage. It runs the length of the body and provides
structural support, preceding the development of the vertebral column in most vertebrates.
The spinal cord, on the other hand, is part of the central nervous system and is a long, thin,
tubular structure made up of nervous tissue, which extends from the medulla oblongata in
the brainstem to the lumbar region of the vertebral column. The diagram you described likely
shows the distinction between the nerve cord (which will develop into the spinal cord in
vertebrates) and the notochord, reinforcing that they are not the same structure.
In chordates, one of the defining characteristics or synapomorphies is the presence of a
dorsal nerve cord, which is a neural tube located above the notochord. This nerve cord is
eventually developed into the central nervous system, which includes the brain and spinal
cord in vertebrates. The notochord acts as a scaffold for the development of the vertebral
column and is located ventrally to the nerve cord.
The answer C: "No, because it totally disappears after embryonic life" is actually not
accurate in the context of human biology. The notochord does not entirely disappear;
remnants of it persist into adulthood. In humans, parts of the notochord remain and
contribute to the nucleus pulposus of the intervertebral discs, as mentioned earlier.
So, while the notochord itself as a whole structure does not persist beyond the embryonic
stage, its remnants are indeed present in the adult body within the intervertebral discs. This
is why the correct answer is B, "Yes, because it becomes the intervertebral discs," because it
speaks to the notochord's role in the adult human body, even though it is not present in its
original form.
The answer A: "sponge" is correct.
Sea squirts, also known as tunicates or Urochordata, feed by drawing water in through their
incurrent siphon, filtering out plankton and other nutrients, and then expelling the filtered
water through their excurrent siphon. This mode of feeding is similar to how sponges feed,
as they also draw in water to filter out food before expelling the water. Both use a filtering
system to capture food from the water that flows through them. Bivalves, annelid fan worms,
gastropods, and sea jellies have different feeding mechanisms that do not primarily involve
filtering water through their bodies.
The answer B: "The woodland hypothesis" suggests the idea that early tetrapods, which had
limbs that could not support their weight on land, might have used their limbs for other
purposes rather than walking on land, such as navigating through dense vegetation or
woodland environments. This contrasts with the "shrinking waterhole hypothesis," which
posits that limbs evolved for walking on land as a response to desiccating pools in a drying
environment, necessitating the movement from one water source to another over land.
Given the statement that early tetrapod legs could not support their weight on land, it implies
that these limbs were not initially used for terrestrial locomotion but perhaps for other
functions such as maneuvering through shallow water or vegetation, which aligns with the
woodland hypothesis.
In general, when humans have migrated to new areas, there have often been significant
impacts on local faunas. Extinction events due to human activity are typically more
pronounced on landmasses that were isolated and then later settled by humans. Among the
options provided:
Africa is the cradle of humanity, and while it has seen extinctions, its fauna evolved
alongside humans and may have been less impacted compared to other continents where
humans arrived much later.
Asia has also had a long history of human habitation, though its vastness and variety of
ecosystems mean that human impacts have varied greatly across the continent.
Australia saw a significant number of extinctions coinciding with the arrival of humans. Its
highly endemic mammalian fauna was quite vulnerable to human activities.
North America also experienced a wave of extinctions that coincided with human arrival.
Among these, Australia is often cited as having a very high rate of extinction due to human
activities, especially since its isolated fauna had evolved in the absence of humans and thus
were highly susceptible to the impacts of human settlement. If the graphic you're referencing
displays this type of information, it would likely show Australia as having a large number of
extinctions directly attributed to human arrival. However, without seeing the image, I cannot
confirm this; the answer would be based on the data presented in your specific figure.
"Synapomorphy" refers to a derived trait that is shared by two or more taxa and is used to
infer a common ancestry. In this context, "HOX LIKE GENES," "EMBRYO WITH
BLASTULA," and "COLLAGEN IN EXTRACELLULAR MATRIX" can indeed be considered
synapomorphies of many animal groups, indicating a shared evolutionary origin.
"Animals main features" refers to the general characteristics that are common to the animal
kingdom. HOX like genes, embryos that develop through a blastula stage, and the presence
of collagen in the extracellular matrix are key features that distinguish animals from other life
forms.
So, if both "Synapomorphy" and "Animals main features" are the answers you're referring to,
it seems the question may be looking for characteristics that are both defining of animals
broadly and indicative of a shared evolutionary heritage within the animal kingdom. These
features are not unique to any one group such as Porifera or Mollusks, but rather are shared
across many animal taxa.
The features listed:
"CHOANOCYTES" are flagellated cells that line the body cavity and are characteristic of
sponges, where they generate water flow and filter food.
"SPICULES" are structural elements found in sponges that provide support and deter
predators.
"NO TRUE TISSUE" indicates that the organism does not have tissues organized into
organs and systems. Sponges are known for this lack of true tissues—they are at a cellular
level of organization.
Given these characteristics, the correct answer from the provided choices is:
C. Porifera
These are distinguishing characteristics of the phylum Porifera, which includes sponges.
These features set Porifera apart from other animal phyla and are not synapomorphies, as
they are not shared derived traits that can be used to infer common ancestry between
multiple taxa.
E. Distinguishing
The term "distinguishing" would be used here to indicate that these features are distinctive of
the phylum Porifera compared to other phyla.
So, the correct answers provided are C. Porifera and E. Distinguishing, as these features
uniquely identify sponges within the animal kingdom.
The features you've listed are characteristic of the phylum Cnidaria:
"RADIAL SYMMETRY IN ADULT" indicates that the body plan of the organism can be
divided into similar halves by any longitudinal plane passing through the central axis.
"2 TRUE TISSUE LAYER" refers to the presence of two germ layers in the body, the
ectoderm and the endoderm, which is a feature of diploblastic organisms.
"CNIDOCYTES" are specialized cells that cnidarians use for capturing prey and defense.
They contain structures called nematocysts, which can deliver a sting.
"MEDUSA AND POLYP" are two distinct life cycle stages found in cnidarians. The medusa is
typically the free-swimming jellyfish stage, and the polyp is often sessile.
Given these characteristics, the correct answer is:
C. Cnidaria
These features distinguish cnidarians from other animal groups.
E. Distinguishing
The term "distinguishing" applies because these traits are used to differentiate cnidarians
from other phyla, such as Mollusks and Annelids, which have different body plans, tissue
organization, and lack cnidocytes.
Hence, C. Cnidaria and E. Distinguishing are the correct answers, as these features are
distinctive of the Cnidaria phylum.
The features listed here are characteristic of the phylum Platyhelminthes (flatworms):
"3 TISSUE LAYERS" refers to the presence of three germ layers: the ectoderm, mesoderm,
and endoderm, which makes an organism triploblastic.
"NO COELOM" means that there is no true body cavity within the mesoderm, a
characteristic known as acoelomate.
"INCOMPLETE GUT" refers to a digestive system with only one opening that serves as both
mouth and anus, known as a gastrovascular cavity.
Given these characteristics, the correct answer is:
A. Platyhelminthes
These features distinguish flatworms from other animal groups.
E. Distinguishing
The term "distinguishing" applies because these traits are used to differentiate the
Platyhelminthes from other phyla that have different body structures, such as coeloms (body
cavities) or a complete gut.
Thus, A. Platyhelminthes and E. Distinguishing are the correct answers, as these features
uniquely identify the Platyhelminthes within the animal kingdom.
The features listed:
"MANTLE" — A significant body structure in certain groups of animals that secretes the shell
in shell-bearing species and contributes to respiration and excretion.
"MUSCULAR FOOT" — Often used for movement and is a common trait in a diverse group
of animals that may use it for locomotion, burrowing, or capturing prey.
"RADULA" — A specialized feeding organ, a toothed, chitinous ribbon, which is used by
mollusks to scrape or cut food before ingestion.
These features are characteristic of the phylum Mollusca:
A. Mollusks — These traits are defining characteristics of mollusks, which include a wide
variety of animals such as snails, clams, squids, and octopuses.
D. Distinguishing — The term "distinguishing" is correct because these traits set the
mollusks apart from other phyla such as Nematodes and Cnidaria, which do not share these
features.
So, the correct answers based on your indication are A. Mollusks and D. Distinguishing. The
presence of a mantle, muscular foot, and radula are distinguishing features of mollusks, and
they are not synapomorphies across multiple animal phyla, as nematodes and cnidarians do
not possess these structures.
The features listed:
"UNIQUE SEGMENTATION" refers to the division of the body into multiple similar units or
segments.
"BRISTLES OR SETAE" are hair-like structures that can be found in various forms on
different animals; in some phyla, they are specifically associated with locomotion or
sensation.
These characteristics are distinctive of:
A. Annelids — This phylum includes segmented worms such as earthworms and leeches,
which are known for their body segmentation and the presence of setae (bristles) that aid in
locomotion.
E. Distinguishing — These traits are distinguishing features of annelids, setting them apart
from other phyla such as Nematodes and Platyhelminthes, which do not exhibit the same
type of segmentation or setae.
The correct answers you've indicated, A. Annelids and E. Distinguishing, are accurate
because these features specifically identify annelids within the animal kingdom. They are not
common to Nematodes or Platyhelminthes, nor are they synapomorphies that would apply
across multiple animal phyla.
The features listed:
"PSEUDOCOELOM" is a body cavity that is not completely lined with mesoderm, which is
characteristic of certain invertebrate animals.
"SIMPLE MUSCULATURE AND MOVEMENT" suggests a more basic structure for muscle
tissue and less complex movements.
These characteristics are distinctive of:
A. Nematodes — Also known as roundworms, this phylum is known for having a
pseudocoelom and simple muscle structure, which allows for the thrashing movement they
are known for.
E. Distinguishing — These features are used to distinguish nematodes from other phyla.
Porifera (sponges) do not have a body cavity or true musculature, and arthropods have a
coelom (in the form of a hemocoel) and more complex musculature.
Therefore, the correct answers, based on the traits given, are A. Nematodes and E.
Distinguishing. These feat
The features listed are characteristic of the phylum Arthropoda:
"HARD CUTICLE" — Arthropods have an exoskeleton made of chitin, which serves as a
hard protective layer.
"PAIRED JOINTED APPENDAGES" — This includes legs, antennae, and other structures,
allowing for a wide range of movements and functions.
"COMPOUND EYES" — Many arthropods have eyes composed of numerous tiny lenses,
offering a broad field of vision.
"SEGMENTATION" — Arthropods exhibit segmented bodies, though the degree of
segmentation can vary significantly across different groups within the phylum.
"TAGMATIZATION" — This refers to the specialization of body segments into functional
groups called tagmata (e.g., head, thorax, abdomen).
Given these characteristics, the correct answer is:
A. Arthropods — These features distinctly identify arthropods, which include insects,
arachnids, crustaceans, and myriapods.
E. Distinguishing — These traits serve to distinguish arthropods from other animal groups,
such as Annelids (segmented worms) and Porifera (sponges), which do not share these
specific features.
Therefore, the correct answers you've identified, A. Arthropods and E. Distinguishing, are
accurate because these features specifically and uniquely describe the phylum Arthropoda
within the animal kingdom.
The features listed are characteristic of the phylum Chordata:
"NOTOCHORD" — A flexible rod that provides support, found at some stage in the
development of all chordates.
"DORSAL HOLLOW NERVE CHORD" — A nerve cord that is located above the notochord
and develops into the spinal cord and brain in many chordates.
"POST ANAL TAIL" — A tail that extends beyond the anus, present at some stage in the
development of all chordates.
Given these characteristics, the correct answers are:
A. Chordates — These features uniquely identify chordates, distinguishing them from other
phyla such as Cnidaria and Platyhelminthes.
D. Synapomorphy — These traits are synapomorphies for the phylum Chordata, meaning
they are shared derived traits that are used to infer a common ancestry among all chordates.
Therefore, the correct answers, A. Chordates and D. Synapomorphy, accurately reflect that
these features are both defining of the phylum Chordata and represent shared evolutionary
traits among its members.