Bellwork: Why are cells in the human body so small Bellwork: Why are cells in the human body so small? What advantages and/or disadvantages does this provide?

Cell growth, division and reproduction Section 10.1

Why do cells divide rather than continue growing? The larger the cell the more demands on it’s DNA DNA like a library of information If too many users, not enough books to teach everyone

Why do cells divide rather than continue growing? A large cell is inefficient at moving nutrients and waste across the cell membrane It’s all about surface area to volume ratio

Large cells would be like congested towns/cities

How to cells overcome these issues? As they get larger they divide Two daughter cells are formed via cell division DNA is replicated Surface are to volume ratio is increased Efficient exchange of materials

Asexual vs sexual reproduction Common with single celled organisms Genetically identical offspring are produced from one parent cell Occurs in multicellular organisms

Asexual vs sexual reproduction Two parent cells fuse together Special reproductive cells fuse together, and offspring are produced Genetic material comes from both parents Most animals and plants undergo sexual reproduction

Asexual vs sexual reproduction Asexual = survival strategy in single celled organisms Fast reproduction = more likely to survive This assumes conditions remain favourable, what happens if they change? Sexual reproduction – take a lot longer Can be useful if seasonal changes affect food availability Increases genetic diversity Increased resistance to disease, changes in condtions Darwinism Some organisms, like yeast can do both