Asexual Reproduction

S Illustrate and explain the process of mitotic cell division in plants and animals. Vocabulary & People InterphaseMitosisIPMAT Cytokinesis Asexual Binary FissionBudding SporeFragmentation

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 chromatids separated 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

InterphaseProphaseMetaphase Parent cell Copied and condensed Lining up AnaphaseTelophaseCytokinesis Pulling apart Nucleus forming Identical daughter cells You 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 PMATPMAT

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 organisms clones are vulnerable to disease/environment Little possibility for evolution clones 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 ChromosomesDNAGenes TraitHeredityInterphase MitosisCytokinesis Asexual Binary FissionBudding SporeFragmentation