ANIMAL SURVIVAL REPRODUCTION Mr G Davidson

Reproduction All living things reproduce and produce offspring similar to themselves. If they did not reproduce, their numbers would decrease and they would become extinct.

Sexual Reproduction Sexual reproduction involves the meeting of 2 sex cells called GAMETES. The male gamete is called the sperm. The female gamete is called the egg. This meeting and joining is called FERTILISATION.

Fertilisation Fertilisation can either be INTERNAL or EXTERNAL. External fertilisation is usually found in water based animals. The gametes meet outside the body of the parents, e.g. trout. The eggs are released into the water and the sperm are released over the top of them. Large numbers of both are produced due to the high chance of failure as well as the high mortality rate.

Fertilisation Internal fertilisation is usually found in terrestrial animals (Land based). It still requires the presence of a fluid for the sperm to swim in. The sperm fertilises the egg inside the body of the female.

Human Reproduction A male mammal has a special organ called a penis for placing sperm into the female. During copulation the penis is inserted into the female’s vagina. Sperm are released into the vagina.

Human Male Reproductive System Testis Sperm duct Penis Seminal vesicles Urethra Prostate gland Foreskin Scrotum

Human Female Reproductive System Oviduct Uterus Ovary Vagina Cervix Labia

Fertilisation Fertilisation is when one sperm fuses with one egg. The sperm loses its tail and the male nucleus joins the female nucleus. A membrane called the FERTILISATION MEMBRANE then forms round the fertilised egg, preventing other sperms from entering.

Fertilisation In both types of fertilisation there is an attraction between the sperm and eggs. The sperm swim towards the egg for fertilisation – in land animals they swim in a fluid called SEMEN.

Fertilisation Internal fertilisation is more efficient because the eggs are protected inside the body of the mother. Fewer eggs are produced and the gametes are closer together and therefore the chances of fertilisation are greater.

Fertilisation After fertilisation, the fertilised egg called a ZYGOTE begins to divide and the first division results in 2 cells being formed. Further divisions increase the number to 4 then 8 and so on until a ball of many cells is produced.

Human Development Human females produce one egg per month in a process called OVULATION. The egg, released by the ovary, passes into the fallopian tube (oviduct) where fertilisation may occur. The zygote divides and the ball of cells produced becomes implanted into the wall of the uterus.

Human Development After the zygote has implanted into the wall of the uterus it begins to grow and develop. A special structure called the PLACENTA develops, allowing the blood of the mother and embryo to come very close without mixing. The embryo is attached to the placenta by the UMBILICAL CORD. The placenta allows the mother and embryo to exchange essential materials.

Human Development

Human Development

Trout Development Trout breed during the month of November. After fertilisation occurs, the trout eggs begin to develop. Living organisms grow and develop at different rates. During this time many changes may occur before the organism becomes sexually mature and capable of reproduction.

Trout Growth Rate Age (years) Length (cm) 1 5 2 18 3 22 4 30 32 6 34 7 36 8

Trout Growth Rate

Trout Growth Rate Between which years did the trout grow fastest? At what age did it reach full size? Suggest what size it will be in 10 years. Years 1 & 2 Year 7 36 cm

Survival Chances Many gametes and young don’t survive reproduction. Only the fittest offspring survive to produce more of the species. Different groups of animals produce different amounts of eggs.

Total No. of eggs produced Survival Chances Total No. of eggs produced No. of eggs fertilised No. of eggs diseased No. of zygotes eaten No. of young eaten Rabbit 8 4 Trout 3000 2000 200 800 850 Pheasant 15 12 2 3 Human 1 Frog 1000 750 50 400 Calculate the percentage survival rate of each animal.