Lecture 27 Animal Reproduction

Question 1

Animal reproduction

Answer 1

A population outlives its member only by reproduction, the generation of new
individuals from existing ones

Question 2

Objectives for Reproduction

Answer 2

Differentiate reproduction strategies and advantages

Understand the importance of coordination for fertilization

Connect concepts across the module

Question 3

Sexual reproduction

Answer 3

by fusion of haploid gametes, male
sperm and female eggs, to form a
diploid zygote

Question 4

Asexual reproduction

Answer 4

without the fusion of egg and sperm

Question 5

Hermaphroditism

Answer 5

An individual animal produces both male and female gametes

Any two individuals can mate under this system, and in some species, hermaphrodites can also self-fertilize

Question 6

Mechanisms of Asexual reproduction

Answer 6

Fission, Fragmentation, Budding, Parthenogenesis

Question 7

Fission

Answer 7

separation of a parent into two or more individuals of about the same size.

Question 8

Fragmentation

Answer 8

breaking of the body into pieces, which develop into adults.

Question 9

Budding

Answer 9

new individuals arise from outgrowths of existing ones

Question 10

Parthenogenesis

Answer 10

is the development of a new individual from an unfertilized egg

Question 11

The animal sexual life cycle

Answer 11

slide 10

Question 12

The cost of sexual reproduction: sexual vs asexual

Answer 12

Sexual reproduction is the creation of an offspring by fusion of haploid gametes, male sperm and female eggs, to form a diploid zygote.

Sexual females have half as many daughters as asexual females; this is the “twofold cost” of sexual reproduction.

Despite this, almost all eukaryotic species reproduce sexually.

slide 11

Question 13

The advantage of sexual reproduction

Answer 13

● Sexual reproduction may enhance reproductive success of parents when environmental factors change relatively rapidly.
● This is due to their production of genetically varied offspring.
● Asexual reproduction is expected to be most advantageous in stable, favorable environments.

Question 14

Fertilization

Answer 14

The number of chromosomes in a haploid cell is 23. n=23. n=46

slide 15

Question 15

Gametogenesis

Answer 15

the production of gametes

Question 16

Spermatogenesis

Answer 16

the formation of sperm, is continuous and prolific.
● Hundreds of millions of sperm are produced per day; each sperm takes about 7 weeks to develop.

Question 17

Oogenesis

Answer 17

the development of a mature egg, is a
prolonged process.
● Immature eggs form in the female embryo but do not complete their development until years or decades later.

Question 18

Testes: Spermatogenesis

Answer 18

The male gonads, = testes, consist of highly coiled tubes surrounded by connective
tissue

Question 19

seminiferous tubules

Answer 19

where sperm forms

Production of normal sperm cannot occur at the body temperatures of most mammals.

Question 20

scrotum

Answer 20

where the testes of many mammals are held outside the abdominal cavity

temp is lower than in the abdominal cavity

Question 21

Hormonal control of the testes

Answer 21

slide 19

Question 22

Female ovary: Oogenesis

Answer 22

slide 20

Question 23

Oogenesis starting at puberty

Answer 23

slide 21

Question 24

Spermatogenesis versus oogenesis

Answer 24

Spermatogenesis differs from oogenesis in three ways:
● All four products of meiosis develop into sperm, while only one of the four becomes an egg.
● Spermatogenesis occurs throughout adolescence and adulthood.
● Sperm are produced continuously without the prolonged interruptions in oogenesis.

Question 25

Fertilization

Answer 25

● Formation of a diploid (2n) zygote from a haploid egg and sperm ● Depends on mechanisms that bring together sperm and eggs of the same species ● Two types ○ External fertilization ○ Internal fertilization

Question 26

External fertilization

Answer 26

● Eggs shed by the female are fertilized by sperm in the external environment. ● A moist habitat is required ○ allow sperm to swim to the egg ○ to prevent the gametes from drying out.

Question 27

Coordination

Answer 27

Timing is crucial to ensure that mature sperm and eggs encounter one another. ● Some species with external fertilization exhibit spawning, in which individuals cluster in the same area to release their gametes into the water at the same time. ● In some cases, chemical signals trigger spawning; in others, environmental cues are responsible. ○ “courtship” behaviors leading to the fertilization of the eggs of one female by one male

Question 28

Internal fertilization

Answer 28

● An adaptation - enables sperm to reach an egg despite a dry external environment. ● Requirements ○ Behavioral interactions ○ Compatible copulatory organs. ● Mating animals may make use of pheromones, chemicals released by one organism that influence the physiology and behavior of individuals of the same species

Question 29

Reproductive anatomy of the human female

Answer 29

slide 29

Question 30

Fertilization and implantation

Answer 30

1.ovulation 2.fertilization 3.cleavage 4.cleavage continues 5.implantation slide 30

Question 31

what is the Acrosomal Reaction

Answer 31

the moment a sperm head contacts the egg surface, molecules in the jelly coat trigger the acrosomal reaction in the sperm. ● The Cortical Reaction Model organism: Sea urchin fertilization

Question 32

The acrosomal reaction ex

Answer 32

● Discharge of hydrolytic enzymes from the acrosome ● Digest the jelly coat, enabling a sperm structure called the acrosomal process to form, elongate, and penetrate the coat. ● Molecules and events at the egg surface play a crucial role in each step of fertilization: ○ Sperm penetrate the protective layer around the egg. ○ Receptors on the egg surface bind to molecules on the sperm surface.

Question 33

Polyspermy

Answer 33

the entry of multiple sperm nuclei into the egg changes in the egg surface prevents this

Question 34

The acrosomal and cortical reactions during sea urchin fertilization

Answer 34

slide 33

Question 35

Cortical reactions

Answer 35

Sperm binding triggers a cortical reaction, ● Depolarisation of membrane - fast block ● the release of enzymes from cortical granules to the outside of the cell. ● catalyze changes in the zona pellucida, ● slow block to polyspermy. (No fast block to polyspermy is known in mammals.)

Question 36

Fast block

Answer 36

immediately but temporarily blocks additional sperm from fertilizing the egg

Question 37

Slow block

Answer 37

gradually establishes a permanent barrier to sperm entry

Question 38

Changes in the uterus

Answer 38

define the menstrual cycle (also called the uterine cycle)

Question 39

Changes in the ovaries

Answer 39

define the ovarian cycle

Question 40

The reproductive cycles of the human female part 1: FSH and LH levels

Answer 40

slide 37

Question 41

Ovarian cycle and hormones

Answer 41

slide 38 When estradiol secretion by the follicle begins to rise steeply, FSH and LH levels increase markedly. The maturing follicle enlarges to form a bulge at the surface of the ovary. The follicular phase ends at ovulation, and the secondary oocyte is released. The luteal phase follows ovulation.

Question 42

Uterine cycle and hormones

Answer 42

slide 40

Question 43

Anterior pituitary hormones

Answer 43

slide 41, 42, 43 1. The ovarian cycle begins when the hypothalamus releases GnRH. 2. The GnRH stimulates the anterior pituitary to secrete small amounts of FSH and LH. 3. FSH stimulates follicle growth, aided by LH 4. The follicles start to make estradiol

Question 44

The uterine cycle

Answer 44

Hormones coordinate the uterine cycle with the ovarian cycle: ● Thickening of the endometrium during the proliferative phase coordinates with the follicular phase. ● Secretion of nutrients during the secretory phase coordinates with the luteal phase. ● Shedding of the endometrium during the menstrual flow phase coordinates with the growth of new ovarian follicles. slide 45

Question 45

Implantation: in the uterus

Answer 45

slide 46 the embryo implantation into the endometrium

Question 46

Contraceptive methods

Answer 46

slide 47 and 48

Question 47

In vitro fertilization (IVF)

Answer 47

slide 49 and 50