AIM: How Is Internal Fertilization and Development Different from External

Fertilization and Development

Sexual Reproduction:

Sperm

A fertilized egg cell is called a ZygoteCharacteristics of Sexual Reproduction:1) Is the creation of a new individual from

parents2

2) Offspring are not genetically to the parents

identical

23 + 23 46

Egg Zygote

Fertilization

INTERNAL FERTILIZATION• Eggs and sperm meet inside the female’s body

• Occurs in most land vertebrates

• Ex. Reptiles, birds, mammals

EXTERNAL FERTILIZATION• Eggs fertilized

outside female’s body

• Occurs mostly in aquatic environments

–Ex. Fish, amphibians

• HAZARDOUS – many eggs and sperm are produced so some survive

• Eggs and sperm may not meet, they may be eaten or environmental conditions may change

Embryonic DevelopmentAn embryo is a developing offspring.

Development can be either INTERNAL or EXTERNAL, depending on the organism.

What is the difference between internal and external

development?

What is the difference between internal and external

fertilization?

INTERNAL DEVELOPMENT

• Embryo develops inside the female, placenta provides nourishment

Human Fertilization• Internal fertilization – male

penis is used to introduce sperm into female’s vagina.

Where does fertilization usually occur?

• Fertilization occurs in the fallopian tubes (oviduct)

How many eggs are released a month by a female?

Normally one egg is released per month, however, sometimes TWO can be released at the same time.

Ovulation

What happens after fertilization?

The embryo travels to the uterus and implants itself in

the uterus lining