Sexual Reproduction in Animals

Male Female

Gamete – sperm

Gonad – testes

Many sperm cells

- spermatogenesisSperm cells are(n) haploid/monoploid

Gamete – egg

Gonad – ovary

Few to many eggs

- oogenesisEgg cells are (n) haploid/monoploid

Sperm

*Smaller

*Swims through liquid

*Head, middle, & tail (flagellum)

Egg

*Larger than a body cell

*Cannot move on its own

*Round shape

Fertilization

• Sperm nucleus enters the egg and moves to the egg nucleus. The 2 nuclei join together and then form a zygote.

External Fertilization*outside the body

• Animals that breed in the water

• Many hazards in the environment– Sperm and egg may not meet– Eggs or offspring may be eaten– May die due to environmental conditions

• Temperature• Oxygen level

• Large number of sperm and egg are released to overcome hazards

• Hormones control behavior to have sperm and egg released at the same time.

Internal Fertilization*within the female body

• Land animals

• Some aquatic animals– Shark– Octopus

• Requires specialized sex organ to carry sperm to body of female

• Watery environment needed for sperm to swim to the egg

• After fertilization, zygote is enclosed in a protective shell and released OR remains and develops in female body

Zygote

Turtle laying eggs

• Internal Fertilization– Fewer eggs needed– Well protected – Increased chance of fertilization

Parthenogenesis – development of unfertilized egg into an adult.- Bees & Wasps