Reproduction in vertebrates

Reproductive strategies between different species.

Reproductive strategy

structural, functional and behavioural adaptations that improve the chances of fertilisation and the survival of offspring

external fertilisation

fertilisation that takes place outside the female’s body, usually in water

internal fertiliation

fetilisation that occurs inside the female’s body where the male has deposited its sperm

ovipary

eggs are laid; the embryo develops outside the mother’s body

ovovivipary

young develop from eggs fertilised internally and retained within the mother’s body after fertilisation until they hatch

vivipary

the young develop inside the uterus of the mother after eggs are fertilised internally; young are nourished through the placenta

amniotic egg

the embryo inside the egg is protected by a hard shell; the egg consists of many extra-embryonic membranes that serve different functions

extra-embryonic membranes

membranes that surround the developing embryo inside the amniotic egg or uterus

amnion

produces amniotic fluid which cushions embryo and protects it from mechanical injury, temperature changes, dehydration

allantois

collects the embryo’s nitrogenous waste and assists in the exchange of gases

chorion

allows for gaseous exchange in the amniotic egg and forms the placenta in mammals

yolk sac

contains the food reserves for the developing embryo

precocial development

when hatchlings are well developed as they hatch, able to move and feed themselves, with eyes open - limited parental care

altricial development

when hatchlings are underdeveloped as they hatch, unable to move or feed or fend for themselves - young require more parental care

parental care

includes the building of nests, protection, teaching of young and feeding - the care, or lack thereof, directly influences the survival of the young

feritilisation

occurs when a sperm cell and egg cell fuse to form a zygote

hardened calcareous or leathery shell

The shell helps protect the developing embryo from mechanical injury and prevent desiccation, while still allowing gases to move through

gamete

an egg or sperm cell with half the number of chromosomes

gametogenesis

the process in which gametes are produced in the testes and ovaries through meiosis

oogenesis

the process that occurs when egg cells are made in the ovary through meiosis

spermatogenesis

the process that takes place when sperm cells are made in the testes through meiosis

germinal epithelium

cuboidal epithelium found on the surface of the testes and ovaries which give rise to the cells which mature to form sperm cells and egg cells respectively

testes

produces sperm cells and the hormone testosterone

scrotum

protects the testes and holds the testes “outside” the body, at 2°C lower than body temp

epididymis

temporarily stores spermatids until they mature into sperm cells

vas deferens

transports sperm from the epididymis to the urethra

urethra

transports urine and semen out of the body

prostate gland

produces a nutrient-rich fluid that provides energy for the sperm cells

Cowper’s glands

produces mucus that helps with the movement of sperm cells

seminal vesicles

produces alkaline fluid to neutralise vaginal acids which would kill sperm

testosterone functions

development of the male secondary sexual characteristics and stimulating the maturation of sperm cells