BIO 2 Animal Diversity

Characteristic of animals

• Multicellular eukaryotes

• Heterotrophic

• Move at some stage in their life cycles

• Despite very different lifestyles and physical appearances, DNA overwhelmingly confirms

• evolution from a common ancestor

blastula

early embryonic stage; hollow ball

blastopore

a special region on the surface of an early embryo that typically becomes one of the ends of the intestinal tract (mouth or anus)

germ layers

special groups of cells in embryos that develop into different types of tissues and organs

Asymmetry

cannot be separated into equal parts

Bilateral (symmetry)

can be split into 2 “sides” only along 1 plane

• homologous trait

Radial (symmetry)

body organized around a central axis

protostomes

• has to have bilateral symmetry

• the blastopore becomes the “mouth first”

deuterostomes

• has to have bilateral symmetry

• the blastopore becomes the “mouth second” (anus develops first)

ectoderm (embryonic germ layer)

“outside”; dermal tissues, neural tissues

endoderm (embryonic germ layer)

“inside”; gut lining

mesoderm

“middle”; connective tissues (e.g. muscle, blood)

Phylum Porifera (sponges)

• Lack germ layers, tissues, organs, and mouth

• Simplest body design

• Asymmetric

• Almost all marine

• Outer body layer is only a single cell thick

• filter feeders

Collar cells

are specialized cells that pull water into the sponge and capture food particles

phylum cnidaria

• jellyfish, corals, anemones

• Defined tissues and organs (nervous, digestive, reproductive)

• Radial symmetry

• Digestive system has only 1 opening like a pouch - food enters mouth and digestive waste leaves via mouth (gastrovascular cavity)

• capture food with stinging cells (cnidocytes)

cnidarian body forms

• medusa (jelly fish like)

• polyp (hand like)

phylum platyhelminthes (flatworms)

• Flatworms (platus = flat)

• No circulatory system

• Digestive tract, if present, forms a gastrovascular cavity (no anus) that branches throughout their body

• tapeworms are flatworms without a gut

phylum annelida (segmented worms)

• Earthworms, leeches, polychaetes

• Body comprised of repeating, similar units (segments)

• possess both mouth and anus (complete digestive system)

• No respiratory system – rely on diffusion of gases through skin

• closed circulatory system

closed circulatory system

blood is FULLY contained in vessels

phylum nematoda (roundworms)

• No segments!

• No circulatory or respiratory systems (rely on body surface

for gas exchange)

• complete digestive tract

• Periodically shed nonliving cuticle (made of chitin)

• More related to arthropods (e.g. insects) than other worm phyla

Ascaris lumbricoides (a roundworm)

• parasitic intestinal nematode

1. Eggs are ingested

2. They hatch and travel to the lungs in blood vessels

3. Cough, cough...swallow!

4. Reproduce in intestines

5. Eggs released in feces

phylum mollusca

• shellfish, squid, snails

• Protostomes

• Most have shells

• 3 major classes : Gastropoda (snails), Bivalvia (shellfish), and Cephalopoda (squid, octopus)

• Open circulatory system

Open circulatory system

blood is not completely contained in blood vessels but directly bathes organs in a hemocoel

Class gastropoda (mollusca)

• Snails, slugs, sea slugs

• Sea slugs and slugs lack shells

class bivalvia (mollusca)

• clams, oysters, mussels

• Hinged shells

• Lack a head

• Gills are used to filter feed as well as gas exchange

class cephalopoda (mollusca)

• squid, octopus, nautilus

• Very mobile, short-lived, well-developed nervous systems

• Only molluscs with closed circulatory systems

phylum arthropoda

• insects, crustaceans, spiders, millipedes, and centipedes

• Segmented bodies typically divided into head, thorax, and abdomen

• exoskeleton of chitin

1. must be molted to allow growth

2. Protective

3. Limits water loss (waxy)

4. Jointed and highly “customizable”

• open circulatory system

metamorphosis (arthropods)

• Stages of development

1) Larva – feeding stage

2) Pupa – resting stage in which metamorphosis, the

transformation from larva to adult, occurs

3) Adult

This is indirect development, where larvae and adults are very different in appearance.

phylum echinodermata

• sea stars, sea cucumbers, and sea urchins

• deuterostomes

• None live in fresh water

• internal skeleton of calcium carbonate

• Adults → radial

• Larvae → bilateral

water vascular systems

• only in echinoderms

• Hydraulic system comprised of tubes and tube feet

• performs gas exchange, locomotion, feeding

phylum chordata

• possess a notochord

• deuterostomes

• 4 primary features

1. Notochord – dorsal, supportive rod

2. Dorsal, hollow nerve cord

3. Pharyngeal slits (form gills in some animals)

4. Post-anal tail

• 3 subphyla: Urochordata (tunicates), Cepahalochordata

  (lancelets), and Vertebrata

notochord

• 1st structure to develop in chordate embryos

• sits below a dorsal, hollow nerve cord

• Stiffens the body and provides a place for muscles to attach

subphylum vertebrata

• protective cartilage or bone protects the brain, and skeletal elements protect the dorsal, hollow nerve cord

• in most vertebrates, the vertebrae replace the notochord as the animal becomes an adult

• Early vertebrates were jawless, a trait still seen in lampreys and hagfish

hagfsh

• Jawless fishes

• Have no fins or limbs

• feed on dying or decaying animals in ocean

• Skeleton is cartilage

• Adults retain notochord

cartilaginous fish

• sharks, rays, and skates

• have jaw

ray-finned fishes

• have jaw

• Bony skeletons

• Bony rays support fins

• swim bladders

swimbladder and lung

related structures

lobe-finned fish

• coelacanths and lungfishes

• swimbladder

• Thick, jointed bones in fins rather than thin bony

rays a step toward weight-bearing legs

challenges to life on land

• Air is not very supportive

1. four limbs (tetrapod)

2. Vertebral column that transmits weight to ground

• Respiration requires moist surfaces, and air is very dry

1. Internal lungs keep moisture minimize evaporation of water

• Developing young must be protected from dry air

1. Shelled, waterproof, amniotic egg

class amphibia (vertebrata)

• First tetrapods (4-footed animals)

• use lungs and skin to respire

• Almost exclusively confined to moist environments

1. Skin → very thin and gas-permeable

2. Eggs → surrounded by a thin membrane

amniotes (group)

• Amniotic egg

• Fertilization inside female body rather than in water

• Thicker skin, hair, scales, or feathers skin prevents water loss

• Excretory systems that conserve water

class reptilia (vertebrata)

• Lizards, snakes, turtles, birds

• scales

• Birds

• subgroup of reptiles adapted to flight

1. wings = modified forelimbs

2. wing bones → hollow

3. Large breastbone supports flight muscles

4. Feathers = modified scales

• endothermic (“warm blooded”) animals supports highly active lifestyles (warmer temperatures = faster chemistry)

class mammalia (vertebrata)

1. Sweat glands

2. Mammary glands

3. Hair

• young of most develop within the mother’s uterus

• endothermic

period

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