Learning Objectives: I can explain…  …how Sexual Reproduction is different from Asexual Reproduction.  …how sex cells are created and how this is different from how regular body cells are created.  …how organisms created through sexual reproduction compare to their parents.

Sexual Reproduction two different parents New organism is produced when sex cells from two different parents join together. DIFFERENT Offspring that are produced by sexual reproduction have DNA that is DIFFERENT compared to both of its parents.

Most plants and animals reproduce in this manner. Remember what we call the reproductive part of a plant? Remember what we call the reproductive part of a plant? Flowers! Sexual Reproduction

sperm testes Males make one kind of sex cell, called the sperm. These are produced by the testes. egg Females make one kind of sex cell, called the egg. These are produced by the ovaries. Sex cells are usually different in size.

Sperm are small, with all of the genetic material crammed into the “head”.

Eggs are large. Why might this be so? Electron microscope picture of egg

Once two sex cells have joined, we say that fertilization has occurred.

The new cell that forms is called a zygote.

If you have an egg cell with 10 chromosomes joining a sperm cell with 10 chromosomes, how many chromosomes will the new baby cell (the zygote have)? 20

A human body cell has 23 pairs of chromosomes, but a human sex cell has only 23 individual chromosomes. So….your sex cells have a way to reduce their chromosome number…it is called MEIOSIS, or reduction division.

Reproductive System by Brainpop 1.What are the male reproductive organs called? 2.What are the female reproductive organs called? 3.Women are _______ with all their eggs.

Fetal Development by Brainpop 1.What do we call a fertilized egg cell? 2.What do we call the hollow ball that develops several days after fertilization occurs? 3.What do we call a baby about 2 weeks after fertilization occurs?

MEIOSIS MEIOSIS (MY-OSIS) Process that produces sex cells There are two rounds of cell division in this process Occurs in the reproductive organs of plant or animal

MEIOSIS (MY-OSIS) Reduces the chromosome number for pairing up later MEIOSIS I and MEIOSIS II Happens through 2 divisions of the nucleus, called MEIOSIS I and MEIOSIS II

Cells that are the same as the parent cell Cells that are different from the parent cell (half the number of chromosomes). These will become SPERM (if you are a boy) or EGGS (if you are a girl) *just like Mitosis See Meiosis in Action!!! Another Animation DNA is copied normally DNA is NOT copied in this round. Instead, cell just split in half.

Meiosis Videoclip Meiosis Clip Meiosis (Greatest Biology Discoveries with Bill Nye) Meiosis

Down’s Syndrome Trisomy 21: 3 copies of the 21 st chromosome