Animal Reproduction

Question 1

What is Asexual Reproduction?

Answer 1

Reproduction leading to genetically identical offspring; no genetic diversity, but energetically inexpensive. A relatively faster process.

Question 2

What is Sexual Reproduction?

Answer 2

Diploid individuals (2n) produces haploid sex cells (n) [gametogenesis]. Haploid sex cells (n) unit to form new diploid individual [fertilization]. 
Genetic diversity, energetically expensive and relatively slow.

Question 3

What is Budding?

Answer 3

Asexual Reproduction - a new individual arises from an outgrowth of an older one. Common in sponges and some Cnidarians.

Question 4

What is Fission?

Answer 4

Asexual Reproduction - one individual separates into 2 or more individuals of equal size.
Some Cnidarians.

Question 5

What is Fragmentation/Regeneration?

Answer 5

Asexual Reproduction - Individual breaks into small pieces - each piece can form a new individual. Some cells must dedifferentiate.
Echinoderms.

Question 6

What is Parthenogenesis?

Answer 6

Asexual Reproduction - Development of an individual from an unfertilized egg, sometimes also called incomplete sexual reproduction.
Common in Arthropods, some fish, amphibians, and lizards.
Can be used for sex determination (e.g. ants, bees, wasps [social insects], females = diploid [fertilization], males = haploid [parthenogenesis]).

Question 7

What is Cyclic Parthenogenesis?

Answer 7

Some invertebrates alternate between asexual and sexual mode of reproduction depending on the environmental condition.

Question 8

What is an example of Cycle Parthenogenesis?

Answer 8

Daphnia - conditions favourable = parthenogenesis (female)

conditions unfavourable = sexual-mode of reproduction (male, some females)

Question 9

What is Hermaphroditism?

Answer 9

A unique form of sexual reproduction.
Synchronous hermaphroditism = earthworm = both male and female characteristics.
Sequential hermaphroditism = reef fish (pseudochromids) = change sex at some point in their life cycle.
Live in an environment dominated by one sex.

Question 10

What are Protoandrous?

Answer 10

Sequential hermophroditics who were originally male and switched to female.

Question 11

What are Protogynous?

Answer 11

Sequential hermophroditics who were originally female and then switched to male.

Question 12

What are Characteristics of Sexual Reproduction?

Answer 12

Increased Genetic Variability -
1. Independent assortment of homologous chromosomes during meiosis 1 (8.3 million combinations)
2. Crossing over during Prophase 1 (mixing of genes)
3. Random Fertilization (70 Trillion combinations)
More chromosomes = more genetic variability.

Question 13

What is Gametogenesis?

Answer 13

Haploid gametes produced by germ cells in primary sex organs.

Question 14

What are Eggs?

Answer 14

Female haploid gametes produced by ovaries. Large and non-mobile, done through oogenesis.

Question 15

What are Sperm?

Answer 15

Male haploid gametes produced by testes, small and mobile. Produced by spermatogenesis.

Question 16

What is important about Spermatogenesis?

Answer 16

Each diploid parent cell produces 4 sperm cells. Each day, about 3 million primary spermatocytes develop from diploid cells.

Question 17

What is involved in the Endocrine Control of Spermatogenesis?

Answer 17

The hypothalamus (GnRH) stimulates the anterior pituitary, producing LH and FSH. 
LH = Leydig cells (produce, activate, secrete testosterone - indirectly activates spermatogenesis) 
FSH = Sertoli cells (directly activates spermatogenesis)
Negative feedback loops are used.

Question 18

What is important about Oogenesis?

Answer 18

Only 1 ovum is produced in an ovarian cycle. Oogenesis occurs within follicles (layers of tissues).
Full complement of primary oocytes is present at birth and held dormant (in prophase 1) until puberty.

Question 19

What is involved in the Endocrine Control of Oogenesis and Ovulation?

Answer 19

FSH stimulates one follicle to develop (complete meiosis 1) - estradiol stimulates the growth and development of the oocyte; LH triggers ovulation - progesterone prepares the uterus for receiving the embryo.
FSH increases in the blood - spike in estrogen (estradiol) - LH - triggers ovulation.
Positive feedback control (from first spike of estrogen) to hypothalamus; negative feedback control to pituitary.

Question 20

What is Fertilization?

Answer 20

Combining two haploid gametes to form a diploid zygote.

Question 21

What is External Fertilization?

Answer 21

Common in aquatic animals, the haploid gametes are released into the environment, and there they fuse to form a zygote.
There is no risk of desiccation. Potential risks include predation, water currents, and sudden environmental changes; these are compensated by large number of offspring and specific behavioural adaptations.

Question 22

What is Internal Fertilization?

Answer 22

Common in terrestrial animals, the haploid gametes are released inside the animal and fertilization occurs inside the animals.

Question 23

What is the Structure of the Mature Sperm?

Answer 23

Head (Nucleus, acrosome - hydrolyzing enzymes)
Mitochondria (produces the ATP that propels the movement of the tail)
Tail (allows sperm to swim)
Very little cytoplasm

Question 24

What is the Structure of the Mature Ovum?

Answer 24

Zona Pellucida (glycoprotein outer layer, layer that surrounds the plasma membrane)
Cumulus Mass (grows inside a follicle, multiple layers of follicle cells)
Large nucleus
Large cytoplasm

Question 25

What are the general steps of Fertilization?

Answer 25

Haploid egg and sperm unite to form diploid zygote.
Sperm swims toward egg, following species-specific chemical attractant molecules (chemotaxis; drives/guides the sperm toward the egg; high degree of species specificity).
Sperm contact plasma membrane of ova using proteolytic enzymes in acrosome to digest zona pellucida.
Once the sperm fuses with the egg, other sperm are prevented from entering.

Question 26

What are the general steps of the cellular mechanisms of fertilization?

Answer 26

1. The fertilizing sperm penetrates the corona radiate via membrane-bound enzymes in the plasma membrane of its head and binds to ZP3 receptors on the zona pellucida.
2. Binding of the sperm to these receptors triggers the acrosome reaction, in which the hydrolytic enzymes in the acrosome are released onto the zona pelucida.
3. The acrosomal enzymes digest the zona pellucida, creating a pathway to the plasma membrane of the ovum. When the sperm reaches the ovum, the plasma membranes of the two cells fuse.
4. The sperm nucleus enters the ovum cytoplasm.
5. The sperm stimulates the release of Ca2+ stored in cortical granules in the ovum, which in turn inactivates ZP3 receptors, leading to the block to polyspermy

Question 27

What makes sure only one sperm fuses?

Answer 27

The inactivation process of the ZP3 receptors makes sure only one sperm fuses with an ovum.

Question 28

What prevents fertilization of an ovum by the sperm of a different species?

Answer 28

Receptor proteins on ovum prevent fertilization by the sperms of other species; species specificity of sperm-ZP binding.

Question 29

Long-term stress-response are triggered by steroid hormones secreted by the __ __.

Answer 29

Adrenal cortex.

Question 30

The anterior pituitary gland only secretes __.

Answer 30

Peptides.

Question 31

True or False: the Posterior Pituitary Gland synthesizes steroids.

Answer 31

False, the Posterior Pituitary Gland does not synthesize any hormones.