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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
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