Sexual Reproduction

Living Environment

Involves 2 two sexes, Male and Female.Gametes = sex cells – produced in gonads.• Female = ovaries (gonads) produce egg cells

(gametes).• Male = Testes (gonads) produce sperm cells

(gametes)

• Gametes plus other organs necessary to carry out reproduction = reproductive system.

• Examples: uterus, cervix, prostate gland…

Meiosis

• Hermaphrodites – Usually slow moving organisms. Earthworm, snails, hydra…

• Produce both Eggs an Sperm but can not self-fertilize.

• Exchange sperm with another individual to fertilize both eggs.

• Process of Gametes forming in the Gonads• Two types:

– Oogenesis = eggs – spermatogenesis = sperm.

• Eggs are Round– non-motile, nucleus, contain yolk, much larger then

sperm, In humans about 0.1mm in diameter.

• Sperm are Microscopic. – Made up of a tail, neck and head.

• Head is the nucleus which contains chromosomes and an acrosome, which helps the sperm, penetrate the egg.

• • Neck contains mitochondria, which provide energy

• Tail is long and whip like. – Allows sperm to move

Spermatogenesis

Oogenesis

• Fertilization Overview:

Egg + Sperm = Fertilization

(Monoploid) + (Monoploid) = Zygote(Diploid)

Fertilization Step By Step:1. Sperm is released by the male their flagella begin

to beat rapidly pushing them in all directions.

2. Sperm comes in contact with Egg.

3. Acrosome releases enzymes that dissolve an opening through the egg.

4. Head enters the egg while tail remains outside.

5. Head moves towards nucleus of egg.

6. Chromosomes come together.

7. Once egg is fertilized a protective membrane surrounds the zygote, which does not allow any other sperm cells to enter the egg cell.

• Fertilization of a mammalian egg:

• http://brodylab.eng.uci.edu/cgi-bin/jpbrody/animation/files/16-980581646.html

2 Types of Fertilization:

1. External Fertilization – eggs are fertilized in the environment outside the female body. – Can only occur in aquatic environments. Very

hazardous. Increase chances of survival by hormones and quantity.

2. Internal Fertilization – occurs inside the body of the female. Mostly mammals.

– Require specialized sex organs to transfer the sperm from the body of the male to the body of the female.

– Body of the female most be moist so sperm can swim.

– After fertilization zygote forms a hard protective shell and develops outside the female body or remains inside the female body throughout development.

Parthenogenesis

• development of an unfertilized egg

• Occurs in many insects including bees, wasps, and some ants.

Websites

• Mitosis Animation:• http://biology.about.com/library/blmitosisanim.htm• Meiosis Animation:• http://biology.about.com/library/blmeiosisanim.htm• Meiosis written explanation:• http://www.biology.arizona.edu/cell_bio/tutorials/

meiosis/page3.html• Fertilization of a mammalian egg:• http://brodylab.eng.uci.edu/cgi-bin/jpbrody/animation/

files/16-980581646.html