IB Biology HL: Reproduction - D3.1

sexual reproduction

two parents, and uses gametes

asexual reproduction

only one parents, mitosis. chromosomes are identical to parent

internal fertilisation

done in land aminals, as wet environment needed

external fertilisation

done by water animals, such as frogs or fish

animals doing asexual reproduction

• starfish

• sharks

• komodo dragons

• pythons

advantages of asexual reproduction

• very quick

• comparatively lower energy required (no looking for mates)

• more efficient

disadvantages of asexual reproduction

• sum of (negative) mutations

• less genetic variation

• can adapt less quickly

advantages of sexual reproduction

• variation in species is maintained

• best genes manage to reproduce

• better survival rates

Causes of genetic variation in sexual reproduction

• in meiosis 1, genetic material is exchanged between non sister chromatics (not the same) of homologous chromosomes: crossing over

• when members of homologous pairs separate during meiosis 1, maternal and paternal pairs split up: gametes have different variations of homologous chromosomes

adapations of sperm cells

• flagellum to propel cell to egg cells

• mitochondria to perform respiration, produce atp

• acrosome: has enzymes to break down egg cell membrane

• streamlined shape

• no waste of space in head; head mostly nucleus

parts of ovum

• haploid nucleus

• large stores of lipids in cytoplasm

• cortical granules

• layer of protective glycoproteins (zona pellicula)

• layer of follicle cells (corona radiata)

male reproductive system

• bladder: sack that store urine

• penis: used for internal fertilisation, to allow sperm to be as close as possible to egg cells

• prostate: produces fluid that helps in transport and nurishment of sperm

• sperm duct: transports sperm from testes to urethra

• epididymis: store sperm (right behind testicles)

• testis: outside the body to prevent overheating

• urethra: releases urine from bladder and sperm from seminal vesicle

• erectile tissue: part of penis, artery at the base of penis, which when needed will bring much blood, increasing tension

female reproductive system

• vagina; opening for penis, to allow internal fertilisation

• cervix: way from vagina to uterus

• fallopian tubes: site where fertilisation happens, attachment where ovary attaches to uterus

• ovaries: site of egg production and maturation

hermaphrodites

an organism with both female and male reproductive parts

example of hermaphrodite animals

• earthworms

• snails

• banana slugs

primordial follicle

bunch of small cells surrounding actual egg cell, before having matured.

the follicle doesn’t get released, and it breaks down into a corpus luteum

ovarian cycle

• follicular phase ( follicle maturation )

• ovulation phase ( mature follicle gets release )

• luteal phase ( corpus luteum gets broken down

uterine cycle

• menstruation: uterine lining breaks down and gets thinner

menbrane thickens, 14 days in ovulation occurs, 28 days if no fertilisation membrane breaks down as decrease in hormones

LH

luteinizing hormone: made by the pituitary gland. Promotes ovulation and the formation of the corpus luteum. stays relatively constant, when it peaks is ovulation

FSH

follicle stimulating hormone: made by pituitary gland. Promotes development of the follicles in the ovary. Peaks when ovulation occurs

estrogen

made by the developing follicle and corpus luteum in the ovary. promotes thickening of uterine lining. level of oestrogen is increasing as follicle develops. Peaks right before ovulation

progesterone

made by corpus luteum. maintains thickened uterine lining. Increases right after ovulation

whole process of menstrual cycle

• drop in progesterone = menstruation

• FSH stimulates development off follicule in the ovary: follicle starts developing

• the follicle produces aestrogen which stimulates the thickening of uterine lining

• the peak of LH stimulates ovulation at day 14

• corpus luteum starts disintegrating but continues releasing progesterone

• progesterone increases, which maintains uterine lining

• eventually decreases