DO NOW: What is better: sexual DO NOW: What is better: sexual or asexual reproduction? or asexual reproduction?

Mitosis Vs. MeiosisMitosis Vs. MeiosisThere are two types of cell

division that allow organisms to grow in size and in number.

Cell division: the separation of one cell into two

2 types of cell division: ◦Mitosis◦Meiosis

MitosisMitosisMitosis: makes

body cells and helps the organism to grow in size by producing TWO identical diploid cells

A type of asexual reproduction

Produces Diploid cells: a cell with two copies of each chromosome (2N)

1. 1. INTERPHASEINTERPHASE 3 Different Phases:◦G1 Phase: Period when cell growth and development occur

◦S Phase : DNA Replication / synthesis occurs

◦G2 Phase: Organelles needed for cell division are made (Centrioles and Spindle Fibers)

2. PROPHASE2. PROPHASEThe longest phaseChromosomes

appearCentrioles move to

opposite ends of the cell

Chromosomes attach to the spindle

Nucleolus and nuclear membrane breaks down

3. METAPHASE3. METAPHASE

Shortest phase of mitosis

Chromosomes line up at center of the cell

4. ANAPHASE4. ANAPHASECentromeres splitSister chromotids separate to form individual chromosomes

Anaphase ends when the movement of chromosomes stops

5. TELOPHASE5. TELOPHASEChromosomes uncoil into chromatin

Nuclear membrane reforms

Spindle breaks apart

MeiosisMeiosisMeiosis: makes

sex cells and helps an organism to reproduce by producing different haploid cellsHaploid: a cell with one copy of each chromosome (N)Male vs. Female: Meiosis produces 4 sperm cells in males and ONE egg cell in females

Why meiosis?Why meiosis?

Meiosis consists of two separate divisions, known as meiosis I and meiosis II.

Meiosis I begins with one diploid (2n) cell.

By the end of meiosis II, there are four haploid (n) cells.

These haploid cells are called sex cells— gametes.

Male gametes are called sperm.

Female gametes are called eggs.

When a sperm fertilizes an egg, the resulting zygote once again has the diploid number of chromosomes.

This pattern of reproduction, involving the production and subsequent fusion of haploid sex cells, is called sexual reproduction

Comparing Mitosis and MeiosisComparing Mitosis and Meiosis

Mitosis Meiosis

Number of cell divisions? 1 2

Exchange of genetic material? No Yes, crossing over!

Number of functioning cells produce?

2 4 sperm in males1 egg in females

Offspring are.. Identical to original

Highly variable and diverse, contain half of the genetic information of the original

Purpose? Growth or replacement of body cells

Combine to form the zygote for reproduction

Pros and ConsPros and ConsMitosis Meiosis

Positives Repair old or damaged cells

Make exact copies

Varied offspring

Species is more stable

Negatives Organisms are all the same so one disease can wipe out an entire population

Requires 2 parents

More time consuming