Zoology Review

Growth & Reproduction

Animal Growth

• Young animals have a period of rapid growth

• Growth occurs when cells reproduce more quickly than they die

• Cell division that results in body growth is called mitosis

Five stages of mitosis

• Interphase – – resting

• Prophase – – chromosome formation

• Metaphase – – chromosome alignment

• Anaphase – – chromosome separation

• Telophase – – Cell division

Growth

• Mitosis is most active in young animals

• Growth – cell masses expand the tissues– Tissues make up organs– Organs make up systems– Systems make up organisms

Animal Reproduction

• New organisms are created by the joining of reproductive cells called gametes

• Gametes are formed by meiosis

• Gametes are haploid cells– Only contain ½ of genetic material required for

life

• Parent cells are diploid

Fertilization

• Male and female gametes form a single cell – called a zygote

• Zygotes are diploid

• Many variations in development

• Study of development is embryology

• Fertilization may occur inside or outside of the body

Mammals

• Eggs are fertilized inside of the body

• Zygotes develop to various stages of maturity inside the mother

• Most young are born very dependent on maternal care

• Varying degrees of development at birth

Amphibians & most fish

• Fertilization occurs outside of the body

• No maternal care

• Some fish give birth to live young

Birds & Most Reptiles

• Fertilization occurs inside the body

• Fertilized eggs are covered with a protective shell as they pass thru the ovaduct

• Eggs are laid to complete development

• No or little maternal care

• Some snakes give birth to live young