Chapter 32

Page 1

A. Animal Characteristics

i. Animals are all multicellular

ii. All are chemoheterotrophs

iii. Most ingest their food (some absorb)

iv. They have no cell walls, they do have a plasma membrane

v. They use structural proteins for support

a. Includes collagen and keratin

vi. Most animals have a nervous system as well as a muscular system

vii. Not all animals have tissues

viii. Most animals utilize sexual reproduction, although asexual reproduction is not rare

a. Some do both depending on their life cycle

ix. Male reproductive cell is the sperm: small, motile and flagellated

x. Female reproductive cell is the egg: large and non-motile

B. Animal Development

i. The haploid reproductive cells fuse to form a zygote

a. The zygote starts dividing and forms into a blastula: a multicellular hollow ball

b. There is no growth at this point, only division into smaller cells

ii. Gastrulation occurs next, forming embryonic tissues: stage called gastrula

iii. Many animals have a larval stage: early non-reproductive stage

a. Has a different environment, look and food source

b. butterfly v. caterpillar, frog v. tadpole

C. Animals

i. Tissues: a group of cells with similar structure and function

ii. Parazoa: animals without tissues

a. no tissue = no organs or organ systems

b. sponges are the only living example

iii. Eumetazoa: animals with tissues

a. all animals except sponges

b. jellies have tissue but no true organs

* parazoa and eumetazoan are descriptive terms not taxonomies

D. Animal Symmetry

i. Eumetazoa are divided into 2 groups based on their symmetry

a. Radial symmetry

1. have a top and bottom but no head/rear no left/right

2. live in water

3. Radiata: jellyfish and comb jellies

b. Bilateral symmetry

1. Two-sided symmetry

2. has left/right, top/bottom, front/back etc.

3. Tend to concentrate sensory organs in their anterior end

-cephalization

E. Tissues

i. During gastrulation different layers of tissue develop

ii. Ectoderm

a. Outer layer

b. Give rise to the outer covering of animals

c. Hair, reptile scales and feathers

iii. Mesoderm

a. Between the ectoderm and endoderm

b. Forms the muscles and many of the organs

c.* Not found in the radiata (cnidarians and ctenophores) bilateral only

iv. Endoderm

a. Inner layer

b. Gives rise to the digestive tract and associated organs

F. Body cavities

i. Bilateral animals are further divided into 3 different groups based on body cavities

ii. Acoelomates

a. Have a solid body with no cavities between the layers of tissue

b. Flatworms

iii. Pseudocoelomates

a. Have a cavity between the endoderm and mesoderm called pseudocoelom: false cavity

b. Rotifers and roundworms (nematodes… not segmented)

iv. Coelomates

a. Most bilateral animals

b. Have a body cavity: coelom surrounded by the mesoderm

G. Protostomes and Deuterostomes

i. Is this a real distinction?

ii. Two different groups of coelomates based on embryonic development

a. The zygote cleavage of protostomes is spiral and determinate

b.The zygote cleave of deuterostomes is radial and indeterminate

iii. The process of gastrulation forms the first opening: the blastopore

a. In protostomes the blastopore develops into the mouth

b. In deuterostomes the blastopore develops into the anus