Methods of Asexual Reproduction This is what it would look like if humans reproduced by...

Methods of Asexual Reproduction

This is what it would look like if humans reproduced by fragmentation!

Budding

• A new organism grows on another one and then separates from the parent organism only when it is mature.

• Examples of organisms that reproduce by budding include: yeasts, sponges and hydra

bud

bud

bud

Binary Fission

• Division into two parts (daughter cells) which each daughter cell has the potential to grow to the size of the original cell (parent cell)

• An example of an organism that reproduces by binary fission is a paramecium.

Daughter cells

Regeneration

• When an animal that is capable of regeneration loses a body part, it can grow a replacement part.

• If the lost body part contains enough genetic information from the parent, it can regenerate into an entirely new organism.

• Echinoderms and the hydra in molds are examples of organisms that reproduce by regeneration.

Fragmentation

• A new organism grows from a fragment of the parent.

• Each fragment develops into a mature, fully grown individual.

• Examples of organisms that reproduce by fragmentation include: molds and planaria.

Vegetative Reproduction

• New individuals are formed without the production of seeds or spores

• May produce bulbs, tubers or rhizomes (runners)

• Examples of organisms that reproduce by vegetative reproduction include: tulips, dahlia, strawberries

rhizome

bulb

Vegetative Propagation

• The production of a new plant from a portion of another plant, such as a stem or branch.

• Examples of organisms that reproduce by vegetative propagation include: spider plants, potatoes, aloe and various other plants.

New spider plant

cutting

Spores

• In some organisms, meiosis leads to the formation of haploid spores rather than gametes. These spores grow into multicellular individuals without being fertilized.

• Examples of organisms that reproduce by forming spores include: mushrooms, molds and ferns

spores

Asexual Reproduction

Method Number of

Parents

Genetics Pros Cons

Asexual 1 parent • Identical• 100% of

genes come from 1 parent

• No mate• Identical

to parent

• Mutations are definite

• No variety

Sexual Reproduction

Sexual Reproduction• Two parents

• Genetically speaking, the

offspring get info from both

parents:

½ from mother (egg)

½ from father (sperm)

There are 46 chromosomes in human cells,

so 23 from mom + 23 from dad = 46 total

Sexual Reproduction

• Requires sex cells (gametes)– Male sex cell (gamete) – sperm– Female sex cell (gamete) – egg

• Fertilization is the process in which sperm and egg unite– Chromosomes double

Ex) 2 + 2 = 4

Cell division by mitosisCell division by mitosis

• Mitosis is cell division of body cells

• Mitosis produces exact copies of the parent cell

• The new daughter cells have the diploid number of chromosomes

Step 3 Chromosomes line up along the middle of the cell and each centromere attaches to a spindle fiber.

Step 4

Spindle fibers go to work like tugboats, pulling each pair towards opposite ends of the cell.

Step 5 Nuclear membrane returns around

Meiosis• Cell division that

results in the formation of gametes (sex cells)– Sperm and egg– Cells are haploid

• Cells are NOT identical– Each cell contains half

the number of chromosomes but not necessarily the same chromosomes as the others

How many chromosomes?

• Humans have 23 pairs of chromosomes like these

• The diploid number of chromosomes is

23x2 = 46

• Sex cells (gametes) have 23 single chromosomes - the haploid (half) number

So……what’s the point?So……what’s the point?

• An egg cell is haploid

• A sperm cell is haploid

• When they join at fertilization the resulting cell is diploid

• This makes a full set of instructions to make a new organism!

Mitosis vs Meiosis