Reproduction

Question 1

Asexual or clonal reproduction mechanisms

Answer 1

Fission, budding, fragmentation

Some reproduce via an egg but without fertilisation e.g. bees and aphids - parthogenesis

Question 2

Sexual reproduction

Answer 2

Creates genetic variation via fusing of gametes produced during meiosis.
Competitive advantage of 2 parents so that at least some offspring will grow and reproduce in a changing environment.

Question 3

Strategies used to ensure evolutionary fitness

Answer 3

Synchronisation of gamete release to increase chances of fertilisation
Allow competition to determine sexual selection between males for the same female

Question 4

External fertilisation, risks and strategies

Answer 4

Sperm must swim to egg, that uses attractants. Risks:
Waves may separate gametes
Strategies: vast numbers, cycles of breeding, amplexus where male clings to female and squeezes out eggs through cloata

Question 5

Oviparous

Answer 5

e.g. hens lay eggs and monotremes i.e. mammal produce milk but oviparous e.g. duck-billed platypus - all food within egg

Question 6

Viviparous

Answer 6

e.g. humans, give birth to live young after being growth in mother, eutherian placental animals (real placenta) and marsupials which give birth to live young and have mammary glands by no true placenta so babies born at a much less developed stage

Question 7

Ovoviviparous

Answer 7

e.g. some fish, lizards, amphibians, snakes

Retain fertilised egg in body but all nutrients from egg not mother

Question 8

Strategies to ensure survival and competition

Answer 8

Brown garden snails have courtship displays involving shooting love darts into each other that increase sperm counts
Sea urchins get together in large groups to mate - kin selection in close knit communities - look after others if relates -> altruistic
No parental care = more offspring
Lots of parental care = fewer offspring

Question 9

Monogamy

Answer 9

One partner at a lime, often for life, e.g. birds

Question 10

Promiscuous

Answer 10

Free for all, male investment low. Live in large groups - kin selectin

Question 11

Polyandry

Answer 11

Rare - 1 female and many males e.g. mole rats

Question 12

Polygamy

Answer 12

Males mate with more than one female - 80% mammals, intense male competition - female has most investment

Question 13

Haremes

Answer 13

e.g. seals = element of female choice, but also competition between males e.g. peacocks shiny bright feathers - shiny if healthy

Question 14

Sexual dimorphism

Answer 14

Differences in size and colour increase mating success to attract mate and support egg production. Include different appearance of genders for identification, bigger bodies female for eggs and antlers, showing off and other males that isn’t herd

Question 15

Simultaneous hermaphroditism

Answer 15

Both mature egg and sperm in same organic, - can choose which one but cant fertilise themselves, increasing chance of success

Question 16

Sequential hermaphroditism

Answer 16

A change from one gender to another (only one at a time) - protogynous = female first; protandrous = male first

Question 17

Levels of sex determination

Answer 17

Genetic - recomb of X and Y
Gonadal - testes or ovaries present determined by Y chromosomes
Phenotypic - apparent anatomic sex not always true

Question 18

Congenital adrenal hyperplasia

Answer 18

Inherited enzyme problem in biosynthesis of cortisol. The deficient of 21 beta-hydroxylate leads to a reduction in cortisol and build up of androgen steroid precursor from adrenals - masculinised features of a female

Question 19

The Guevedoces of Dominican republic

Answer 19

Born looking female, then develop a scrotum and penis at puberty due to a deficient of 5-paha reductive which is the active precursor in production of testosterone.

Question 20

When does sexual differentiation take place in development?

Answer 20

Early. Biopotential gonad has outer cortex and inner medulla. Sex determination depends on pre scene of SRY gene - TDF activates additional genes (testes), testes produce AMH, DST and testosterone.

Question 21

Gonads

Answer 21

Pair of testes in male, ovaries in female

Function - produce gametes

Question 22

Reproductive tract

Answer 22

System of specialised ducts for transporting or housing gametes

Question 23

Accessory sex glands

Answer 23

Produce supporting secretions into tract

Question 24

In males…

Answer 24

testes, accessory = seminal besicales, bulbourethral glands, prostate gland, penis, tract = epididymis, bas dederens, urethra

Question 25

In females…

Answer 25

Ovaries, tract = oviducts (fallopian tubes), uterus, cerix, vagina, vulva

Question 26

Gametogenesis

Answer 26

The production of gametes is under complex endocrine control. Sex steroid hormones derived from cholesterol.

Question 27

Glands for production of sex hormones

Answer 27

Hypothalamus, pituitary, gonads

Question 28

Hypothalamopituitarygonoadal axis

Answer 28

Pulsatile release of GnRH from hypothalamus causes secretion of LH and FSH from pituitary which act on testes to bring about testosterone production -> spermatogenesis

Question 29

Testosterone

Answer 29

95% from testes, 5% adrenal glands in males. Acts on reproductive system before emirs to masculinise tract and promote decent of testes into scrotum. Has effects on sex-specific tissues after birth - puberty, spermatogenesis an maintenance of tract.
Secondary sexual characteristics: male hair growth, deep voice, muscle growth
Develops sex drive and controls gonadotropin
Promotes bond growth and epiphyseal fusion, causes aggression

Question 30

Spermatogenesis

Answer 30

Mitotic and meiotic division and cytodifferentiation. Highly specialised (tail, many mitochondria, acrosome) to carry genetic material considerable distance. Spermatozoa krrp close association with sertoli cells during development. 1 spermatogonim:4 spermatozoa.
Sperm stored and concentrated in epididymis and ducts deferens.

Question 31

During ejaculation…

Answer 31

Sperm mixed with secretions from accessory glands. Seminal vesicles - fructose for energy and prostaglandins providing movement. The prostate alkaline fluid neutralises acid in vaginas and clots so sperm doesn’t fall out. PSA breaks down clot after so sperm can move up (mucous production). Release of sperm in a sexual response cycle: excitement, plateau, orgasmic and resolution phases

Question 32

Oestrogen

Answer 32

Causes ova maturation and female secondary sexual characteristics. Also has effects on endometrium and myometrium. Feedback on pituitary gonadotrophins.

Question 33

Progesterone

Answer 33

Effects on endometrium and myometrium (in uterus). Feedback on pituitary and gonadotrophins. Also thermogenic (makes temp rise)

Question 34

Follicular cycle

Answer 34

Primordial follicles begin to enlarge. Day 6 - one dominant remains and some artertic follicles. Oestrogen secreted to circulation from theca internal cells and follicular fluid from granulose cells. Day 14 = ovulation.

Question 35

Luteal phase

Answer 35

Proliferation of granulose and theca cells giving luteal cells - corpus luteum. Secretion of oestrogen and progesterone and degradation of CL - corpus albicans

Question 36

Menstruation

Answer 36

Day 1-5, proliferative phase including endometrium (little secretion), build up day 5-14

Question 37

Secretory phase

Answer 37

Including vascularisation, coiled glands and secretion of fluid to nature egg day 14-28

Question 38

Uterine endometrium

Answer 38

Glands enlarge. Stratum functional, coiler arteries, straum basal straight basilar arteries, loss of hormonal support (CL) - thinning of endometrium, spasm of arteries, necrosis and sloughing

Question 39

Clinical tests for ovulation

Answer 39

Endometrial biopsy (sample of uterus lining), cervical mucous changes, body temp, hormone levels (LH kits - peak just before ovulation, enzyme immunoassays that detect hormone and mid-luteal progestogens - tells you ovulation has occurred)

Question 40

Hormonal control

Answer 40

Hypothalamus - GnRH brings about anterior pituitary LH and FSH
LH surge caused by switch of oestrogen feedback from- to +. After ovulation = progesterone increase prevents further +ve feedback from oestrogen on LH

Question 41

Primary oocytes

Answer 41

Remain in meiotic arrest until puberty. At the start of each cycle, a few primary oocytes begin to develop, but usually only 1 ovulate per cycle. Natural loss = atresia. 1 oocyte:1ovum. Antrum formation changes shape. What is left of follicles becomes corpus luteum, which provides hormones to keep fertilised egg going. No fertilisation = death of CL

Question 42

Specialised features of eggs

Answer 42

Stored nutrients and factors needed for early embryo development. Egg coat - vitelline coat blocks polyspermy by hardening once fertilised. Chemotaxis attacks sperm tp egg. Protein reasct released by arbacia

Question 43

Drosophila

Answer 43

Produce 1 sperm 3x length of body which blocks female tract so no other males can mate

Question 44

Cast and marmosets

Answer 44

Spines present on penis so that female is locked to male

Question 45

Dragonflies

Answer 45

Spoon shaped end to penis to scoop out sperm from another male

Question 46

Elephants

Answer 46

Reproductive tract ~2m long, testes internal
Males produce sperm from 10-15 years of age - only large bulls can produce
Males has musth - episode of elevated testosterone and aggressiveness with eat-waving musth scent, rumble low frequency noise and musth walk. A cycling female may vocalise and show interest for bulls
Bulls test cow’s readiness to breed by performing flemen behaviour - trunk brings urine samples to receptors in roof of mouth => 1 -3 day window
Cows reproduce from 12-14 years and interval between calves is ~5 years