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