Kingdom Animalia
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Two groups of animals have appeared in the
fossil record, a very ancient one and a more
modern one.
From 700-900 million years ago, a whole world
of animals thrived in the oceans, but their fossils
disappear about 600-650my ago.
A few survived, and became the ancestors of
modern animals.
All modern animals groups can be traced back
to the beginning of the Cambrian Period, about
600 million years ago.
Animalia Traits:
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Heterotrophic--have to ingest (eat) then
digest food
multicellular but NO CELL WALLS
adult is always diploid
motile--can move around
have sexual reproduction
only haploid cells are large, non-motile
eggs and smaller, motile sperm
How we classify animals:
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Symmetry--radial or bilateral
complexity of organism-tissues/organs/systems absent or present
backbone or internal skeleton-absent/present
number of layers developing from zygote
coelom (body cavity) absent/present
segmentation absent/present
Invertebrates vs. Vertebrates
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Does the animal
have a
backbone
(spinal chord) or
some primitive
form of one
during
development?
Ex. those with:
us, fish, sharks
Ex. those
without: jellyfish,
politicians
Sponges
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Sponges-simplest
animals
evolved
multicellularity
get food by
filtering
water for
organic
materials
Jellyfish
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have tissues (but not
organs or systems) and
symmetry
have two layers of tissues
developing from zygote:
endoderm and ectoderm
have nerves and muscles
(both are tissues)
have plant-like alternation
of generations life cycle
Next steps:
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bilateral
symmetry
evolved
Then organs
evolved from
groups of
tissues
Flatworms-forms tubewithin-a-tube
body plan
And then...
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an internal body cavity (a
coelem) for protection of
organs, digestion, and
reproduction
those that did went on to
evolve producing a mouth
(protostomes) or an anus
first and then a mouth
(deuterostomes)
some lower animals
evolved a false coelem, a
pseudocoelem
(=pseduocoelemates): ex.
roundworms
3 groups of protostomes:
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molluscs (snails, squids)
annelids (earthworms)
arthropods (insects, crabs,
spiders)
Molluscs
3 groups within
molluscs:
• 1. Clams, oysters
(bivalves)--filter water
for food.
• 2. Cephalopods
(squid, octopus)--most
advanced molluscs-have closed circulatory
systems and welldeveloped nervous
systems.
• 3. Gastropods (snails,
slugs)-
Some early animals
evolved segmentation
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ex. Annelids
(earthworms)--this
allows specialization
of different segments
for reproduction, etc.
ex. Arthropods
(insects, spiders)-have a tough
exoskeleton for
protection, can
increase body size
through
metamorphosis (like
caterpillarsbutterflies)
Arthropod groups:
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1. Chelicerates-spiders, scorpions,
ticks
2. Crustaceans-shrimp, lobster,
crabs
3. Uniramia-millipedes,
centipedes
4. Insects-grasshoppers, ants,
bees
Deuterostomes--those that
produce an anus
first, then a mouth
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Two groups-echinoderms
(no true
endoskeleton)
and
chordates
(those with
true
endoskeletons
)
Echinoderms
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sea stars, starfish
have a well-developed
coelem and internal
organs
each arm has its own
digestive and
reproductive organs,
and an eyespot at the
end
no respiratory,
excretory, or
circulatory systems-internal water
movement does all
this
Chordates: all have internal
skeletons, plus 3 main
requirements:
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1. A dorsal (back) hollow nerve cord (the
future spinal cord)
2. A notochord--a supporting rod for nerve
cord; notochord later replaced by vertebrae.
3. Pharyngeal pouches--only present in
embryos. In humans, the 1st pair become
ear tubes, the 2nd the tonsils, and the 3rd &
4th become the thymus glands and
parathyroids
Other Chordate traits:
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Usually 2 pairs of
jointed appendages
internal skeleton
that grows with
organism
skull protects brain
complex sensory
organs (eyes, ears,
etc.)
closed circulatory
system
Major Chordate groups:
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1. Fish--3 groups: jawless, cartilage, and
bony.
2. Amphibians--frogs, salamanders
3. Reptiles--snakes, lizards, alligators
4. Birds
5. Mammals
Mammary
glands
Fish: 1st Chordates
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3 groups: jawless,
cartilaginous, and
bony
jawless--ex.
Lamprey eels
cartilaginous--ex.
Sharks, rays
jawed--ex. Salmon,
bass, trout
Fish ancestors,
which were jawless,
evolved the jaw
from modified gill
support bones
Jawed fishes:
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Skeletons of bone
scales made of
modified bone cells
gills covered by
operculum
swim bladders
color vision!
2-chambered heart
with a single loop of
circulation
Amphibians:
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Amphibians are basically
lobe-finned fish that made it
onto land
evolved some unique
features:
1. Tongues
2. Eyelids
3. Ears
4. Voices
5. Highly developed brains
6. Double-loop circulatory
system with 3-chambered
heart
7. But have to return to
water to lay eggs
Birds:
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Kept many reptilian
features, such as
amniotic eggs and
scales (on feet and
face)
only modern
animals with
feathers
endotherms--have
high body
temperature
regardless of
external
temperature
4-chambered
hearts
complete ventilation
Mammals:
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Evolved from “stem
reptiles”
large brain size to body
ratio
have differentiated
teeth
highly differentiated
vertebrae
mammary glands
homeothermy
hair
4-chambered hearts
3 kinds of mammals:
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1. monotremes—lay
eggs
2. marsupials—
embryos have to
crawl to milk glands
located in a pouch
3. placentals—
embryos attach via
placenta to mother for
nutrition; completely
enclosed until birth
Placental mammal groups:
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Rodents--mice, beavers; large front teeth
hoofed mammals--horse group and cow
group
rodent-like--rabbits
carnivores--dogs, cats, bears
cetaceans--whales, dolphins
modified upper lips & noses--elephants
primates-us, chimpanzees, apes
Primates:
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Grasping hands/feet
Binocular vision—allows for 3-dimensional
viewing; helpful in forest environments for
going from tree to tree
Reduction in snout/nose length
Teeth evolved for eating both plant and
animal tissues (=omnivorous)
The
evolutionary
path to us:
700,00
0 years
ago
Human
evolutionary
tree based on
skull
characteristics
1.5
million
years
ago
2.9
million
years
ago