Asexual Reproduction

Cell Division II

S1-1-01 Illustrate and explain the process of mitotic cell division in plants and animals.

Vocabulary & People Interphase Mitosis IPMATCytokinesisAsexual Binary Fission BuddingSpore Fragmentation

All “new” cells (growth, repair or reproduction) are

produced from “old” cells – every cell is either dividing, or

preparing to divide…

Why do cells divide and how does it work?

• Chromosomes look like spaghetti - uncondensed

• Chromosomes copied, cell grows and makes more organelles (preparing to divide)

There is obviously a lot more going on in the cell…but we are just focused on what the

chromosomes are doing during interphase and

mitosis

• Chromosomes become visible – condense• Copied chromosomes pair up – look like an “X”

Centrioles

Sister Chromatids

Centrioles

The condensed copied chromosomes – called sister chromatids – are joined at the middle which is why they have

the X-shape

• Copied chromosomes (sister chromatids) line-up along the middle of the cell

Spindle fibres

Sister Chromatids

Chromosomes are guided into the middle by attached spindle fibres

• Copied chromosomes (sister chromatids) pulled apart towards opposite ends of cell

Sister chromatidsseparated

This is done by the spindle fibres “shortening” and pulling them inwards

Cleavage of cell into two

• Chromosomes back to spaghetti - uncondensed • A new nucleus forms around each set of

chromosomes

Cytokinesis

• Cell membrane grows inwards - pinching into 2

• Each daughter cell has a complete set of the chromosomes – plus organelles and cytoplasm

Leaving 2 identical daughter cells

Interphase Prophase Metaphase

Parent cell Copied and condensed

Lining up

Anaphase Telophase Cytokinesis

Pulling apart Nucleus forming Identical daughter cells

MITOSISYou are expected to be able to identify the IPMAT stage from a picture and draw your own pictures to represent each stage

Why do cells divide?3. Reproduction – Pass on genetic information

There are 2 types of organism reproduction:Asexual and Sexual

1. Rapid and effective reproduction method 2. Cells are “clones” – genetically identical

Asexual Reproduction

• Create offspring from one parent organism• Using basic cell division - Mitosis

Mitosis IS asexual reproduction: making an identical copy (offspring) from an

existing cell (parent)

Types of Asexual Reproduction

1. Binary Fission• Simple single-cell (unicellular) organisms Bacteria have 1 circular chromosome (plasmid)

Remember: even though we call this “binary fission” it is still just a simplified

Mitosis

Bacteria(like E. Coli)

Protists(like amoebas)

Unlike bacteria, these ones actually have a nucleus and a few chromosomes

Telophase, maybe?

2. Budding• Cell duplicates nucleus, forms outgrowth• New cell is not the same size as original cell

Standard mitosis Budding

Fungi(yeast)

The key is unequal mitotic division – think of it as creating a “mini-me”

that will grow bigger…eventually

3. Sporulation• Creation of spores that are released into the air• Spores are made to survive and grow anytime

later

Fungi(mould)

This is similar to budding – but in very large numbers (like creating 1000s of “mini-me’s” at once)

Animals can be split into two big groups:• Vertebrates (with backbones) • Invertebrates (without backbones)

Invertebrates – simple animals – usually reproduce asexually

4. Fragmentation• Ability to regenerate (regrow) fragments of the

body OR have that fragment grow into separate identical organism

The “simpler” the animal the better it will be at fragmentation

Many experiments have been done to investigate

the regeneration and fragmentation of simple

organisms

MITOSIS – in general

Parent cell:Full set of

Chromosomes

2 identical daughter cells

Daughter cells:Full set of

Chromosomes

Remember: ALL these asexual methods of reproduction are just

fancy-named Mitosis

P

M

A

T

PROS – Asexual Reproduction – CONS

Large number of offspring made very quickly

Each offspring will be successful clones are well adapted

Stay close together colonies build if nutrients are present

No need to waste energy finding a sexual partner

No diversity in organismsclones are vulnerable to

disease/environment

Little possibility for evolutionclones are identical

Can lead to overcrowding starvation if not enough nutrients

?

CAN YOU ANSWER THESE QUESTIONS?S1-1-13:How are the terms DNA, chromosome, genes and trait connected?S1-1-01:Why do cells divide and how does it work?

Vocabulary & People Chromosomes DNA GenesTrait Heredity InterphaseMitosis CytokinesisAsexual Binary Fission BuddingSpore Fragmentation