Reproduction and development

Question 1

Parthenogenesis

Answer 1

an example of asexual reproduction in which an egg develops without being fertilised.

In the case of honeybees, males (drones) are fertile haploid adults that arise by parthenogenesis.

In contrast, female honeybees, including both the sterile workers and the fertile queens, are diploid adults that develop from fertilised eggs.

Question 2

Protandrous

Answer 2

males early in dev, females later

e.g. clownfish

Question 3

Protogynous

Answer 3

females when smaller, males when larger, can switch

e.g. Wrasse (fish)

Question 4

hermaphrodites

Answer 4

have both male and female sex organs

Question 5

Long day breeder

Answer 5

mating, laying egg and incubation = summer

growth of offspring = summer

Question 6

Short day breeder

Answer 6

mating, pregnancy, delivery = spread across winter

growth of offspring = summer

Question 7

Asexuality switching

Answer 7

• seasons
• environment
• ratio of males to females etc.

e.g. Daphnia reproduce asexually when environmental conditions are favourable and sexually during times of environmental stress.

Question 8

sexual reproduction

Answer 8

1. the fusion of haploid gametes forms a diploid cell, the zygote.
2. The animal that develops from a zygote can in turn give rise to gametes by meiosis.
3. The female gamete, the egg, is large and nonmotile, whereas the male gamete, the sperm, is generally much smaller and motile.
4. Usually results in only one offspring

Question 9

Asexual reproduction

Answer 9

new individuals are generated without the fusion of egg and sperm.

For most asexual animals, reproduction relies entirely on mitotic cell division, e.g., parthenogenesis.

AsR works best when the environment is stable.

More offspring are produced. (than one)

Question 10

Pheromones

Answer 10

chemicals released by one organism that can influence the physiology and behaviour of other individuals of the same species

Question 11

Fertilisation

Answer 11

Internal
- occurs inside the female
- development occurs inside the body

External
- A moist habitat is almost always required for external fertilisation to prevent the gametes from drying out and to allow the sperm to swim to the eggs
- development occurs outside the body

Question 12

+ and - of Asexual and Sexual Reproduction

Answer 12

diagram ^^

Question 13

marsupials and monotremes

Answer 13

Marsupials e.g. kangaroo - are internally fertilised but then premature embryo is born

Monotremes = echidnas have eggs that are internally fertilised and they lay

• fun fact monotremes don’t have nipples they suck milk from chest hairs

Question 14

Sperm production pathway

Answer 14

seminiferous tubules are part of testes that produces sperm

sperm pass into the coiled duct of an epididymis.

Spermatogenesis produces 4 haploid sperm from one primordial germ cell

Question 15

Oogenesis

Answer 15

• the development of mature oocytes (eggs)
• a prolonged process in the human female. Immature eggs form in the ovary of the female embryo but do not complete their development until years, and often decades, later.
• oogenesis produces only one functional ovum from an oogonium

• cytokinesis is unequal and almost all cytoplasm goes into one egg (three polar bodies - degenerate)

Question 16

Female Reproductive System

Answer 16

• gonads = ovaries
• outer layer of ovary = fossicle
• each fossicle consists of an oocyte, a partially developed egg, surrounded by support cells.
• An oviduct, or uterine tube, extends from the uterus towards a funnel-like opening at each ovary.
• Upon ovulation, cilia on the epithelial lining of the oviduct help collect the egg by drawing fluid from the body cavity into the oviduct.
• Together with wavelike contractions of the oviduct, the cilia convey the egg down the duct to the uterus.
• The inner lining of the uterus, the endometrium, is richly supplied with blood vessels.
• The neck of the uterus, called the cervix, opens into the vagina.

Question 17

Three sets of accessory glands

Answer 17

• seminal vesicles,
• prostate gland,
• bulbourethral glands

Produce secretions that combine with sperm to form semen, the fluid that is ejaculated

Question 18

Male Reproductive System

Answer 18

1. Testes (singular, testis), produce sperm in seminiferous tubules.
2. In humans and many other mammals, testis temperature is maintained about 2°C below the core body temperature by the scrotum.
3. From the seminiferous tubules of a testis, the sperm pass into the coiled duct of an epididymis.
4. During ejaculation, the sperm are propelled from each epididymis through a muscular duct, the vas deferens.
5. The ejaculatory ducts open into the urethra, the outlet tube for both the excretory system and the reproductive system.

Question 19

Sex hormones

Answer 19

1. hypothalamus secretes gonadotropinreleasing hormone (GnRH).
2. This hormone directs the anterior pituitary to secrete the gonadotropins follicle-stimulating hormone (FSH) and luteinising hormone (LH)

Question 20

Steroid Sex hormones

Answer 20

1. androgens produce testosterone;
2. oestrogens produce oestradiol and
   progesterone

Question 21

Ovarian cycle

Answer 21

The FSH, LH and oestrogen levels peak just before ovulation and progesterone will peak post oestrous. Levels will fall if pregnancy does not occur.

After ovulation, the oestradiol and progesterone secreted by the corpus luteum stimulate maintenance and further development of the uterine lining.

The follicular phase of the ovarian cycle is coordinated with the proliferative phase of the uterine cycle.

Question 22

Pregnancy process

Answer 22

1. The zygote begins a series of cell divisions called cleavage
2. about 24 hours after fertilisation and after an additional 4 days produces a blastocyst, a sphere of cells surrounding a central cavity.
3. A few days later, the embryo implants into the endometrium of the uterus.
4. The condition of carrying one or more embryos in the uterus is called pregnancy, or gestation.

Question 23

Fertilisation process

Answer 23

1. sperm makes contact with egg
2. Acrosome releases enzymes which break down the protective membrane
3. plasma membrane of sperm and egg fuse
4. sperm nucleus enters eggs
5. Cortical granules fuse with egg plasma membrane which renders the vitelline layer impenetrable to more sperm.

Question 24

Trophoblast

Answer 24

The outer layer of the blastocyst, the trophoblast, grows outwards and mingles with the endometrium, eventually helping form the placenta

Question 25

Placenta

Answer 25

The placenta transports nutrients, respiratory gases, and wastes between the embryo or foetus and the mother. Materials are exchanged by diffusion, active transport, and selective absorption between the foetal capillary bed and the maternal blood pools.

Question 26

organogenesis

Answer 26

During the first trimester, the blastocyst develops into an embryo which goes through organogenesis, the heart begins to beat, it then becomes a foetus.