REPRODUCTION IN ANIMALS

• Asexual reproduction involves only one parent that produces two or more genetically similar organisms. It occurs mainly in organisms with a simple structure.

• Sexual reproduction involves two parents. A male sex cell joins with a female sex cell (fertilization) and they form a new cell called a zygote. The zygote grows into a new organism.

Binary fission

Budding

Fragmentation

SEXUAL REPRODUCTION

• Two parents of different sex are involved.• The offspring are different from their

parents and from each other

Gonads produce sexual cells.• The gonads in males are the testicles.• The gonads in females are the ovaries.

Sexual cells or gametes.• Ova or eggs, from the ovaries• Sperm cells, from the testes.

MALE FEMALE

GONADS

GAMETES

GAMETES SIZE

GAMETES SHAPE

MOBILE GAMETES?

TYPES OF FERTILIZATIONInternal fertilization •It occurs in terrestrial animals.•The male introduce sperm cells in the female’s body (copulation). •Sperm cells and ova join inside the mother

External fertilization •Occurs in some animals living in water. •The female releases a large amount of ova.•The male releases the sperm cells. •Sperm cells join ova by chance.

EMBRYONIC DEVELOPMENT

Oviparity. Oviparous lay eggs.

EMBRYONIC DEVELOPMENT

Vivipary. The embryo develops inside the body of the mother.

Ovoviviparity. The embryo develops within eggs that remain within the mother's body up until they hatch.

METAMORPHOSISAn animal develops after birth or hatching involving a big change in the animal's form.

COMPLETE METAMORPHOSIS

• Other insects, like beetles, butterflies and flies, are very different from their parents at birth.

• These insects pass through a larval stage, then enter an inactive state called pupa, or chrysalis, and finally emerge as adults.