Sexual/Asexual Reproduction

1. Sexual/Asexual Reproduction

2. Sexual Reproduction • Sexual Reproduction – type of reproduction in which the genetic materials from two different cells combine, producing an offspring • Sperm – male sex cell • Egg – female sex cell • Fertilization– joining of the sperm and egg cell • The new cell that forms is called a zygote.

3. Diploid Cells • Organisms that reproduce sexually make 2 kinds of cells- body cells and sex cells (gametes -sperm & egg) • Diploid cells – cells that have a pair of chromosomes; divide by mitosis (full # of chromosomes) • ex. body cells • Different Organisms have different numbers of chromosomes. • Ex: Humans have 46 chromosomes.(23 pairs) • Homologous chromosomes – pairs of chromosomes that have genes for the same trait arranged in the same order

4. Haploid Cells • Sex cells are Haploid– only have one chromosome from each pair; divide by meiosis (half the # of chromosomes) • ex. sex cells (sperm and egg)

5. Meiosis • Meiosis – process by which one diploid cell divides into four haploid cells; occurs in the formation of sex cells • Meiosis is important because: • It ensures the correct number of chromosomes in offspring • ex. sperm (23) + egg (23) = human (46) • creates more genetic diversity by producing haploid cells.

6. Mitosis vs. Meiosis • Starts as diploid cell • Body cells • 1 division of nucleus • Produces 2 daughter cells • Diploid daughter cells • Used for growth and repair of cells • Starts as diploid cell • Reproductive cells • 2 divisions of nucleus • Produces 4 daughter cells • Haploid daughter cells • Used to produce sex cells

8. Sexual Reproduction +/- • Advantages • Genetic Variation • offspring inherit half their DNA from each parent • helps with adaptations to changing environments • Selective Breeding • breeding species with desirable traits • ex. dog breeding, farming • Disadvantages • Time and Energy • development of sex cells • finding a mate • Exposure to predators, disease, or harsh environmental conditions

9. Asexual reproduction • Asexual reproduction – one parent organism produces offspring without meiosis and fertilization • offspring are genetically identical to parent (clones)

10. Types of asexual reproduction • Fission • simple cell division in prokaryotic (bacteria) cells • Mitosis • simple cell division in eukaryotic cells • Budding • a new organism grows by mitosis on the body of its parent • ex: hydra

11. Types of asexual reproduction • Animal Regeneration • offspring grows from a piece of its parent • Many animals can regenerate damaged or lost body parts. This is not reproduction; new individuals are not produced. • Vegetative Reproduction • offspring grow from a part of a parent plant • Cloning • A type of asexual reproduction developed by scientists and performed in laboratories. • production of an identical individual from a cell, or cluster of cells, taken from a multicellular organism • The clone is a genetic copy of the parent

12. Asexual reproduction +/- • Advantages • no mate required • Enables some organisms to produce a large # of offspring • Disadvantages • little genetic variation which can decrease an organism’s chance of surviving if the environment changes. • more likely to suffer mutations