Topic 12 - Animals I

Question 1

What are the characteristics of animals?

Answer 1

• chemoheterotrophic
• sexual reproduction
• capable of movement

Question 2

Describe the cell structure of animals

Answer 2

• multicellular eukaryotes
• lack cells walls
• nervous & muscle tissue

Question 3

Describe homeobox

Answer 3

highly conserved nucleotide sequence, they are regulatory genes that can turn on and off other genes

Question 4

What are hox genes?

Answer 4

• control anterior to the posterior developmental sequence of the embryo
• the number varies among animal phyla
• is the result of several gene duplication events over evolutionary time

Question 5

Describe the embryonic development

Answer 5

• > diploid zygote undergoes a number of mitotic cell divisions + cleavage
• > cleavage leads to the formation of the multicellular, hollow blastula
• > blastula undergoes gastrulation, forming a gastrula with different layers of embryonic tissue

Question 6

What is protosomia and deuterostomia?

Answer 6

proto: first invagation of the gastrula becomes the mouth
deutero: second invagation becomes the mouth ( first opening becomes the anus, or closes up)

Question 7

Define protosomes

Answer 7

the new row of cells is twisted slightly off-center

• spiral cleavage
• determinant: new cell is destined to form some part of the later embryo

Question 8

Define deuterostomes

Answer 8

each cell division stacks the new cells directly above the previous one

• radial cleavage
• indeterminate: early embryonic cells are not differentiated

Question 9

What is direct development?

Answer 9

embryo continues gradually on towards adult form

Question 10

What is indirect development?

Answer 10

intervening stages whose morphology and behavior differs greatly from sexually mature adult stage

Question 11

What are the different germ layers?

Answer 11

• endo -> digestive tract
• ecto -> outer covering
• meso -> muscle and other organs

Question 12

What is the difference between radiata and bilateria?

Answer 12

radiata: two embryonic cell layers (diploblastic, endo, and ectoderm)
bilateria: three embryonic cell layers (triploblastic, endo, ecto, and mesoderm)

Question 13

What are the two types of symmetry?

Answer 13

• radial, no front or back, left or right

- bilateral, two-sided symmetry

Question 14

What is cephalization?

Answer 14

the concentration of sense organs, nervous control

this is occurring at the anterior end of the body forming the head and brain

Question 15

What are the key innovations in animal evolution?

Answer 15

1. patterns of embryonic development
2. development of different tissues
3. type of body symmetry
4. presence or absence of a body cavity

Question 16

What are the three types of body cavities?

Answer 16

a) coelomate - possess true coelom
b) pseudocoelomate - lack complete mesodermal lining (middle layer)
c) acoelomate - lacks a body cavity

Question 17

What is the function of coelom?

Answer 17

• cushions internal organs
• allows internal organs to shift without altering the outside of the body
• fluid-filled cavity can be used as a hydrostatic skeleton
• independently gained and lost (evolutionarily) in different animal lineages