BIO 121a Terms compiled based on notes Test and Flashcards

Common Ancestry

All organisms share a universal common ancestor.

Evolution

Change in populations over time due to genetic variation and natural selection.

Natural Selection (VISTA)

Variation, Inheritance, Selection, Time, and Adaptation drive evolutionary changes.

Adaptive Radiation

Diversification from a common ancestor to exploit various ecological niches.

Cambrian Explosion

A period of rapid diversification of multicellular life approximately 540 million years ago.

Gradualism

Slow and steady evolutionary change over time.

Punctuated Equilibrium

Evolution occurs in rapid bursts followed by long periods of stasis.

Symmetry

Body plans of organisms; can be radial, bilateral, or asymmetrical.

Radial Symmetry

Body parts arranged around a central axis, common in cnidarians.

Bilateral Symmetry

Body plan with two symmetrical halves, characteristic of Bilateria.

Diploblastic

Having two germ layers: ectoderm and endoderm.

Triploblastic

Having three germ layers: ectoderm, mesoderm, and endoderm.

Protostome

Animals where the mouth develops from the blastopore.

Deuterostome

Animals where the anus develops from the blastopore.

Phylogenetics

Study of evolutionary relationships among organisms.

Monophyletic

A group consisting of an ancestor and all its descendants.

Paraphyletic

A group that includes an ancestor but not all of its descendants.

Polyphyletic

A group that does not include the most recent common ancestor.

Choanocytes

Collar cells in sponges responsible for water flow and capturing food.

Spicules

Structural elements in sponges made of calcium carbonate or silica.

Cnidocytes

Specialized stinging cells unique to cnidarians.

Nematocysts

Organelles within cnidocytes that deliver a sting to capture prey.

Medusa

Free-swimming, umbrella-shaped body form of cnidarians.

Polyp

Sessile, cylindrical body form of cnidarians.

Cephalization

Evolutionary trend toward a concentration of sensory organs at the anterior end.

Parenchyma

Tissue that fills space between organs in acoelomates like flatworms.

Protonephridia

Primitive excretory structures in flatworms using flame cells.

Torsion

Twisting of the body during gastropod development.

Metamerism

Segmentation of the body into repeated units.

Clitellum

Thickened, glandular section of annelids used for reproduction.

Parapodia

Paired lateral appendages in polychaetes for locomotion and gas exchange.

Water Vascular System

Network of hydraulic canals in echinoderms used in locomotion, feeding, and respiration.

Mutable Collagen

Tissue in echinoderms that can rapidly change stiffness.

Aristotle’s Lantern

Chewing apparatus in sea urchins used for scraping food.

Notochord

A flexible rod that provides support in chordates.

Dorsal Hollow Nerve Cord

Tube-like structure above the notochord; develops into the central nervous system.

Pharyngeal Slits

Openings in the pharynx used for filter-feeding or respiration.

Endostyle/Thyroid

Structure involved in iodine metabolism; precursor to the thyroid gland.

Placoid Scales

Tooth-like scales in cartilaginous fishes.

Lateral Line System

Sensory system in fishes that detects water vibrations.

Ampullae of Lorenzini

Electroreceptive organs in cartilaginous fishes for detecting electrical fields.

Heterocercal Tail

A tail with unequal lobes; provides lift in sharks.

Pulmo-cutaneous Respiration

Gas exchange through lungs and moist skin in amphibians.

Amplexus

Reproductive clasping behavior in frogs.

Paedomorphosis

Retention of juvenile traits into adulthood, seen in some salamanders.

Double Circulation

A circulatory system with separate pulmonary and systemic circuits.

Feathers

Modified scales used for flight, insulation, and display.

Contour Feathers

Streamline the body for flight.

Precocial

Chicks born well-developed and able to feed themselves.

Altricial

Chicks born underdeveloped and requiring parental care.

Exoskeleton

External skeleton made of chitin; provides protection and support.

Ecdysis

Molting of the exoskeleton in arthropods.

Endothermy

Ability of animals to regulate their internal body temperature.

Viviparous

Development of embryos inside the body, with live birth.

Oviparous

Eggs hatch outside the mother’s body.

Ovoviviparous

Embryos develop within eggs retained inside the mother.

Semelparity

Reproduction occurring once before death (e.g., salmon).

Iteroparity

Repeated reproductive cycles throughout an organism's life.

Amniotic Egg

Egg with specialized membranes (amnion, chorion, allantois, yolk sac) for terrestrial development.

Kinetic Skull

Flexible jaw structure in reptiles, especially snakes.

Jacobson’s Organ

Sensory structure in snakes for detecting chemical cues.

Keratinized Skin

Waterproof skin in reptiles and birds made of keratin.

What is the significance of the Cambrian Explosion?

The Cambrian Explosion marks a period approximately 540 million years ago when there was a rapid diversification of multicellular life. Most major animal phyla first appeared during this time, showcasing a wide range of body plans, many of which are still seen today.

How do protostomes differ from deuterostomes?

Protostomes develop the mouth from the blastopore, have spiral and determinate cleavage, and undergo schizocoelous coelom formation. Deuterostomes develop the anus from the blastopore, have radial and indeterminate cleavage, and undergo enterocoelous coelom formation.

What are the key adaptations of amniotes for terrestrial life?

Key adaptations include the amniotic egg with specialized membranes (amnion, chorion, allantois, yolk sac), keratinized waterproof skin, rib ventilation of the lungs, stronger jaws, a high-pressure cardiovascular system, water-conserving nitrogen excretion, and improved sensory systems.

Describe the water vascular system in echinoderms.

The water vascular system is a network of hydraulic canals used for movement, feeding, and respiration. It consists of the madreporite, stone canal, ring canal, radial canals, ampullae, and tube feet. Water enters through the madreporite and is distributed to the tube feet for locomotion and manipulation.

What are neural crest cells, and why are they significant?

Neural crest cells are embryonic cells unique to vertebrates that contribute to the development of sensory organs, skull structures, and the peripheral nervous system. They played a crucial role in the evolution of the vertebrate head and jaw.

How did jaws evolve, and why are they important?

Jaws evolved from modified gill arches in early vertebrates, providing a significant advantage by allowing organisms to grasp, manipulate, and process food more efficiently. This innovation contributed to the diversification of jawed vertebrates (Gnathostomes).

What are the primary differences between amphibians and reptiles in terms of adaptation to land?

Amphibians rely on moist skin for respiration, have aquatic larvae, and exhibit external fertilization. Reptiles have keratinized skin to prevent water loss, amniotic eggs for terrestrial reproduction, and rib ventilation for breathing, making them better adapted to dry environments.

What is countercurrent exchange, and how does it function in fish gills?

Countercurrent exchange is a mechanism in fish gills where water flows opposite to blood flow in capillaries. This arrangement maximizes the gradient for oxygen diffusion, allowing efficient oxygen uptake even in low-oxygen environments.

How do feathers and skeletal adaptations allow birds to fly?

Feathers provide lift, insulation, and streamline the body, while skeletal adaptations like a lightweight, hollow bone structure, fused synsacrum, and keeled sternum for muscle attachment optimize the body for flight. These features reduce weight and enhance power for flying.

Flashcards: BIO 121a Terms compiled based on notes