Meiosis

Meiosis Essential Question Why are the puppies in a litter similar to but not exact copies of each other or their parents?

Reproduction Reproduction in organisms creates offspring- new organisms!

Asexual reproduction: one parent organism produces one or more new organisms that are identical to itself.

Mitosis results in the creation of two daughter cells that are identical to the parent cell.

Unicellular organisms use mitosis to reproduce. The cells in multicellular organisms also use mitosis to reproduce (like your skin cells when you get a cut).

Sexual Reproduction: male and female reproductive cells combine to form offspring with genetic material from BOTH parents.

The male parent contributes a sperm cell and the female parent contributes an egg cell, each of which contain HALF of their genetic material.

When a sperm and egg cell fuse together, they form a cell called a zygote, which develops into the new organism.

A zygote grows and develops into an organism by using mitosis to divide its cells.

Meiosis The process in which reproductive cells divide to form sperm cells and egg cells is called meiosis.

Meiosis ensures that the offspring will inherit the correct number of chromosomes.

Without meiosis, the number of chromosomes would double with each generation.

Meiosis consists of 2 cycles of division, meiosis I and meiosis II Meiosis consists of 2 cycles of division, meiosis I and meiosis II. Before meiosis begins, the DNA is replicated so the cell has two copies of its DNA.

Meiosis I is a lot like mitosis- two daughter cells are made, each with a full set of DNA. UNLIKE mitosis, daughter cells in meiosis I are NOT identical.

Meiosis I daughter cells are not the same because of a process called recombination (genetic reshuffling).

In Meiosis II, the process repeats, but this time the DNA is NOT replicated before the cells divide.

The end result of meiosis II is four gametes, each of which have HALF the amount of chromosomes as the parent cells.

Meiosis

Advantages of Sexual Reproduction Leads to genetic variation Variety of traits in a population of the same species Can help a species survive environmental changes

Advantages of Sexual Reproduction Selective Breeding Offspring with certain desired traits can be made by breeding parents with the preferred traits Results in groups of organisms with similar traits

Disadvantages of Sexual Reproduction Getting a sperm cell and egg cell together to be fertilized can be challenging for some species

Disadvantages of Sexual Reproduction Organisms need time to grow and develop before they are able to reproduce.

What is the cell called that forms from fertilization? Sperm Egg Haploid Zygote

How many daughter cells are produced at the end of meiosis? One Two Three Four

What is one advantage of sexual reproduction? It produces many offspring Offspring are genetically identical Offspring have more genetic variation Can produce offspring quickly

During sexual reproduction, the offspring inherit traits from The mother The father Both parents Themselves

Asexual organisms differ from sexual organisms in that asexual organisms Have no genetic code Do not undergo reproduction Produce a new organism from a single parent Reproduce using cells from two parents