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Evolution, Natural Selection & Genetics (Evolution (Fossils (How they…
Evolution, Natural Selection & Genetics
Evolution
Multicellular life
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Invertebrates came first, then vertebrates
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Plants
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Produced spores then, ~130 million years ago, seed plants emereged
Fossils
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How they form
- Body sinks to sea floor and soft parts rot away
- Body is covered by layers of sediment and lower layers turn to rock from pressure
- Skeleton dissolves leaving a cavity as a mold
- Mineral-rich water fills the mould and the minerals then crystalise leaving a cast
Millions of years later, the sediment is eroded by wind, rain etc... and a fossil is now exposed
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Some can't form because of geo-factors, bad conditions etc...
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Genetics
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Chromosomes & Genes
In a cell, in a nucleolus, as a section of a chromosome
There are 23 pairs of chromosomes (46) except for sex cells. They have 23 chromosomes so they combine to make a zygote of 46 chromosomes
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Alleles
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A recessive allele can only decide your characteristics if it is homozygous (both dominant or recessive in a pair) but a dominant allele will take control if it is a heterozygous pair (one dominant and one recessive)
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Punnet Squares
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Repeated punnet squares using resultant offspring genotypes give you results for higher and higher filial generations
Variation
It is the differences betweeen between organisms of one species based on environmental (continuous) and genetic (discontinuous) factors
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