Kingdom Animalia 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:

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:

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 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 Sponges--

simplest animals

evolved multi-cellularity

get food by filtering water for organic materials

Jellyfish

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: bilateral

symmetry evolved

Then organs evolved from groups of tissues

Flatworms--forms tube-within-a-tube body plan

And then... 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:

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 well-developed nervous systems.

• 3. Gastropods (snails, slugs)--

Some early animals evolved segmentation

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 caterpillarsbutter-flies)

Arthropod groups: 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

Two groups--echinoderms (no true endoskeleton) and chordates (those with true endoskeletons)

Echinoderms 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:

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: 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:

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 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:

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: 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: 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: 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: 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:

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:

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:

Human evolutionary

tree based on skull

characteristics

700,000 years ago

1.5 million years ago

2.9 million years ago