Animal Evolution and Development

Question 1

What was occurring, in terms of life, 700-540 mya?

Answer 1

• Origin of metazoa
• Edicaran fauna
• O2 levels surpass 10%
• Cambrian explosion

Question 2

What kind of life dominated earth for majority of its history?

Answer 2

microbial life

Question 3

Oxygen levels have played a major role in the evolution of life on earth. What has it impacted?

Answer 3

Evolutionary process was greatly accelerated

• more energy from oxidative metabolism
• faster growth and reproduction
• more diversity from sexual reproduction

Question 4

What evolutionary developments have occurred at which oxygen levels?

Answer 4

(Percentages are a percent of present O2 levels)

2. 5% - Eukaryotic Cells
3. 5% - Origin of sexuality
4. 0% - Metazoans

15% - Exoskeletons

35% - First vertebrates

Question 5

When was the ediacaran period? What occurred during this period?

Answer 5

635-542 mya

• avalon explosion
• first animal fossils (no exoskeleton - soft body animal)

Question 6

When was the cambrian period? What occurred during this period?

Answer 6

542-490 mya

• cambrian explosion
• exoskeleton animals - evolved into hard body animals

Question 7

Transitioning from the Neoproterozoic Era to the Paleozoic era (edicarian period to the cambrian period), many changes occurred, what were they?

Answer 7

542 mya over a period of 100 my

• soft bodies (imprints) to hard bodies (fossils)
• collagen synthesis allowed hard parts
• O2 below 5% to O2 above 5%
• 100’s of animal phyla to 34 animal phyla

Question 8

What global mass extinction events have occurred?

Answer 8

6 big ones

Paleozoic Era

• 450-440 mya, 375-360 mya
• End of Permian period, 252 mya, the worst 96% of species killed, set back mammals and ended trilobites

Mesozoic Era

• 201 mya
• End of Cretaceous period (K-T boundary) 66 mya, 75% of species, killed dinosaurs

Cenozoic Era

-10,000 ya-present, holocene extinction All 34 animal phyla survived

Question 9

What were the causes of earlier extinctions?

Answer 9

• Earth icing over
• Plate tectonics causing massive volcanic eruptions
• Meteor impact
• Human impact

Question 10

How have Marine animals been affected by mass extinction events?

Answer 10

Largely unaffected except the Permian extinction killed off large numbers of marine species

Question 11

What animals were killed off by the meteor strike 66 mya?

Answer 11

large animals died, smaller animals were able to shield themselves underground

Question 12

What is the Holocene extinction?

Answer 12

10,000 ya to Present

-Man killing off animals at higher rate than ever

Question 13

What is the summary of animal life on earth?

Answer 13

• 34 animal phyla
• all evolved from common protist ancestor
• all evolved in Ediacaran/Cambrian (600-500 mya)
• all survived since Cambrian (500 mya)
• no new phyla have evolved since cambrian
• lots of families and many classes went extinct during mass extinction events

Question 14

What phyla are we studying?

Answer 14

1. Porifera
2. Cnidaria and Cnetophora
3. Platyhelminthes
4. Rotifera
5. Bryozoa
6. Brachiopoda
7. Mollusca
8. Annelida
9. Nematoda
10. Arthropoda
11. Echinodermata
12. Chordata

Question 15

What is the colonial flagellate hypothesis and what are its steps?

Answer 15

Explanation of the common origin of Metazoa (animals) from protists

1. start with unicellular flagellated protist
2. multiple flagellates make aggregate
3. aggregate form hollow sphere
4. specialized reproductive cells form out of some protists
5. cells begin to fold to make tissues

Question 16

What are the steps in the common developmental sequence of all animals?

Answer 16

1. Gamete formation
2. fertilization
3. cleavage
4. gastrulation
5. oranogenesis
6. growth

Question 17

What occurs during gamete formation?

Answer 17

Gametogenesis

-gametes are produced in

testes - spermatogenesis

in ovaries - oogenesis

Question 18

What provides nourishment to the sperm during spermatogenesis?

Answer 18

the sertoli cell

Question 19

What are the parts of the sperm?

Answer 19

head

midpiece

tail

Question 20

When does meiosis ii occur during oogenesis?

Answer 20

after the secondary oocyte has been fertilized

Question 21

What is ylk for in an egg?

Answer 21

yolk supports embryo through development and different animals have different amounts of yolk

Question 22

What occurs during Fertilization?

Answer 22

Contact and recognition between egg and sperm

• Polyspermy prevention with fast block and fertilization membrane
• Sperm and egg membranes fuse
• sperm tail disintegrates

Question 23

What occurs during Cleavage?

Answer 23

Repeated divisions, converting single large cell, zygote, into many smaller cells called blastomeres

Question 24

What are Isolecithal eggs?

Answer 24

Holoblastic cleavage with equal distribution of yolk because of same size blastomeres

Question 25

What are the the 2 major holoblastic patterns of cleavage?

Answer 25

**Radial Holoblastic Cleavage** -stacked, regulative/indeterminate=deuterostomes **Spiral Holoblastic Cleavage** -close together, mosaic/determinate=protostomes

Question 26

What is the blastula formation during cleavage?

Answer 26

Zygote divided into 100's of cells, which move to form hollow sphere called Blastula. - The fluid filled cavity inside sphere is called blastocoel. - The layer of cells of outside of blastula is the blastoderm, 1 layer of germ cells

Question 27

What is Gastrulation?

Answer 27

Converts spherical blastula into a 2 or 3 layered embryo

Question 28

How is the second germ layer formed during gastrulation?

Answer 28

One pole of blastula invaginates. - the new internal cavity is the archenteron - the opening to the archenteron is the blastopore

Question 29

What are the two possible outcomes of the blastopore during gastrulation?

Answer 29

**Protosomes** - blastopore becomes mouth - spiral, mosaic cleavage **Deuterostomes** - blastopore becomes anus - radial, indeterminate cleavage

Question 30

What are the two germ layers formed during gastrulation?

Answer 30

**Ectoderm** -original germ layer of blastula **Endoderm** -2nd germ layer formed after invagination

Question 31

How many germ layers are present in Diploblastic animals?

Answer 31

2 ectoderm and endoderm

Question 32

How many germ layers are present in Triploblastic animals?

Answer 32

3 ectoderm, endoderm, and mesoderm

Question 33

What is the mesoderm and how does the mesoderm form?

Answer 33

**mesoderm** is 3rd germ layer between ectoderm and endoderm in the blastocoel **In Protosomes** -cells arise from ventral area and move into blastocoel **In Deuterostomes** -central region of archenteron wall pushes outward

Question 34

What occurs during cleavage, gastrulation, and coelem formation for deuterostomes and protosome

Answer 34

Question 35

What occurs during organogenesis?

Answer 35

For Diploblasts, nothing. They don't have organs. -two tissues form germ lines, epidermis and gastrodermis For Triploblasts, organogenesis is the differentiation of 3 germ layers in organs and tissues

Question 36

For triploblasts, what does each germ layer form during organogenesis?

Answer 36

Ectoderm -nervous system, outer epithelium Endoderm -digestive tube, gill arches Mesoderm -skeleton and muscles

Question 37

What are the two types of cleavage that occur?

Answer 37

**Holoblastic** Cleavage - whole **Meroblastic** Cleavage - partial

Question 38

What are the steps of spermatogenesis?

Answer 38

Spermatogonium undergoes mitosis, 2n Produces primary spermatocyte, 2n Primary spermatocyte undergoes meiosis i Produces secondary spermatocyte, 1n Secondary spermatocyte undergoes meiosis ii Produces spermatids, 1n Spermatids undergo differentiation Produces spermatozoa

Question 39

What are the steps of oogenesis?

Answer 39

Oogonium undergoes mitosis, 2n Produces primary oocyte, 2n Primary oocyte undergoes meiosis i Produces secondary oocyte, 1n Secondary oocyte undergoes meiosis ii upon fertilization Produces ovum, 2n