Lecture 22- Asexual and sexual reproduction

Question 1

What are the three types of asexual reproduction?

Answer 1

Budding, regeneration, reparthenogenesis

Question 2

How does budding and regeneration produce new individuals?

Answer 2

Mitosis

Question 3

How does budding work?

Answer 3

A bud grows by mitosis, cells differentiate before the bud breaks away

Question 4

What is regeneration?

Answer 4

• Usually replacement of damaged tissues

- Sometimes pieces of an organism can regenerate complete organisms

Question 5

In what organisms can regeneration be seen?

Answer 5

Echinoderms- each piece including central disk can regenerate
Colonial cnidarians such as corals- pieces broken off in a storm start new colonies
Segmented marine worms break apart

Question 6

What is parthenogenesis?

Answer 6

The development of offspring from unfertilized eggs

Question 7

When is parthenogenesis common?

Answer 7

Arthropods, fish, amphibians and reptiles

Question 8

What can parthenogenesis determine?

Answer 8

Sex- for example, bees:

• Male are haploid
• Females are diploid

Question 9

What happens in some species where the parthenogentic reproduction requires sexual behavior?

Answer 9

Females may act as males depending on cyclical hormonal states (estrogen and progesterone)
The sexual activity stimulates the release of the egg

Question 10

What process produces haploid gametes through meiotic cell division?

Answer 10

Gametogenesis

Question 11

What are the three fundamental steps of sexual reproduction in animals?

Answer 11

Gametogenesis (making gametes)
Mating (bringing gametes together)
Fertilization (fusing gametes)

Question 12

What are the disadvantages of sexual reproduction?

Answer 12

• Time and energy
• Exposes to predators/damage
• Detracts from other behaviors

Question 13

What does sexual reproduction require?

Answer 13

Joining of two haploid cells to form a diploid individual

Question 14

Where does gametogenesis occur?

Answer 14

In the gonads- the testes and ovaries

Question 15

What are the different gametes?

Answer 15

• Small, motile sperm

- Nonmotile ova (eggs)

Question 16

What are gametes produced from?

Answer 16

Germ cells

Question 17

Where do germ cells come from?

Answer 17

They are produced early in the development of the embryo and remain distinct from the rest of the cells

Question 18

Other than germ cells, what are other embryonic cells called?

Answer 18

Somatic cells

Question 19

What happens to the germ cells when gonads begin to form?

Answer 19

They migrate to the gonads

Question 20

Once germ cells are within male gonads, what happens?

Answer 20

They undergo mitosis to produce spermatogonia

Question 21

After germ cells have migrated into female gonads, what happens?

Answer 21

They undergo mitosis to produce oogonia

Question 22

What happens to diploid spermatogonia and oogonia?

Answer 22

They multiply by mitosis to produce primary spermatocytes and primary oocytes

Question 23

What is the next step in gametogenesis after the formation of spermatocytes and oocytes?

Answer 23

Meiosis- reduces chromosomes (haploid cells)

These cells mature into sperm and ova

Question 24

During spermatogenesis, what does the first and second meiotic division produce?

Answer 24

Two secondary spermatocytes

Four haploid spermatids

Question 25

During division of primary spermatocytes, what are the offspring connected by?

Answer 25

Cytoplasmic bridges

Question 26

What happens to spermatids?

Answer 26

They differentiate into sperm

Question 27

What is the first step in oogensis?

Answer 27

The female germ cell divides by mitosis to form oogonia and then primary oocytes

Question 28

What happens to the primary oocyte?

Answer 28

It immediately begins prophase I of meiosis

Question 29

What happens after prophase I of meiosis?

Answer 29

Development stops in many species

Question 30

What happens after development of the primary oocyte stops?

Answer 30

It grows larger and acquires nutrients

Question 31

What happens when meiosis resumes?

Answer 31

The nucleus of the oocyte divides into two daughter cells of unequal size

Question 32

What is the name of the two unequal daughter cells produced by the meiotic division of the primary oocyte?

Answer 32

``` Secondary oocyte (larger cytoplasm) First polar body (smaller one) ```

Question 33

What happens to the secondary oocyte?

Answer 33

It continues with meiosis to form a haploid ootid which differentiates into a mature ovum And a second polar body which degenerates

Question 34

What is fertilisation?

Answer 34

The union of a haploid sperm and a haploid egg to create a diploid zygote

Question 35

What are the 6 steps in fertilisation?

Answer 35

- Recognition of sperm and egg - Activation of sperm - Plasma membranes fuse - Additional sperm entry blocked - Activation of egg - Egg and sperm nuclei fuse

Question 36

How are interactions between sperm and eggs mediated?

Answer 36

Specific recognition molecules

Question 37

What do specific recognition molecules ensure?

Answer 37

The sperm goes towards the egg | The egg isn't fertilised by the wrong species

Question 38

Where is it particularly important eggs aren't fertilised by the wrong species?

Answer 38

Aquatic organisms where sperm and eggs are released to surroundings

Question 39

What adaptation do sea urchins have to make sure fertilisation occurs correctly?

Answer 39

Chemical attractants to increase sperm mobility are species specific Protective layers

Question 40

What two protective layers must sperm pass to get to the egg in marine animals such as sea Urchins?

Answer 40

A jelly coat | Vitelline envelope

Question 41

What is an the membrane enclosed structure on the sperm head?

Answer 41

The acrosome

Question 42

What happens when egg and sperm make contact?

Answer 42

Substances in the jelly coat trigger an acrosomal reaction

Question 43

What happens during the acrosomal reaction?

Answer 43

Membranes in the sperm head and acrosome break down, enzymes are released and digest the jelly coat

Question 44

After a hole has been digested in the jelly coat, what happens?

Answer 44

Actin is polymerized, the acrosomal process extends down from the head of the sperm

Question 45

What is the acrosomal process coated with?

Answer 45

Bindin | A specific recognition molecule

Question 46

Why is the acrosomal process coated with bindin?

Answer 46

Bindin reacts with bindin receptors in the vitelline envelope

Question 47

What happens after bindin binds to bindin receptors?

Answer 47

Sperm and egg membranes fuse to form a fertilisation cone.

Question 48

Internal fertilisation involves...

Answer 48

Specieis specific mating behaviors and egg sperm recognition molecules

Question 49

What is the mammalian egg surrounded by?

Answer 49

Cumulus- cells in a gelatinous matrix

Question 50

What is beneath the cumulus?

Answer 50

The zona pellucida- a glycoprotein envelope functionally similar to the vitilline envelope

Question 51

What happens once sperm has fused and entered an egg cell?

Answer 51

Polyspermy is blocked | Mechanisms prevent entry of more than one sperm to an egg