Some scientists that helped with the theory of natural selection:

Jean-Baptiste Larmack (1744-1829)

• was a french botanist
• believed they inherit traits from the use of body parts (e.g. a giraffe used their necks a lot and that is why they evolved to have longer necks)

Charles Darwin

• proposed theory of natural selection
• similarity between species; common ancestry
• new species form by gradual changes over time
• -> e.g. giraffes with different lengths; long-back giraffes had more of an advantage and would survive longer to pass on traits to offspring. Over time the number of long-necked giraffes would increase
• Charles Darwin used fossils, but because DNA wasn’t discovered at the time, he was unable to convince and prove that his theory was correct. He was also unable to show how there were genetic variations or how alleles were inherited.

DNA

Can be compared to other species; fewer differences means there was less time since they shared an ancestor. 98% of human DNA are similar to Chimpanzees.

Molecular Evidence

• all organisms have a shared number of molecular characteristics; suggeste a shared origin
• DNA and RNA as their genetic material
• Genetic code is universal
• ATP molecule for energy storage
• Proteins made up by the same 20 amino acids (across all animals)
• Phospholids have membranes

Genomics

Genomics is the study of genes in an organism, and the comparison of genes that make up proteins. (I don’t think we need to do this but whatever.)

Okay! So now let’s move onto Natural Selection itself

The Laws of Natural Selection

The laws of natural selection

• There is variation from mutations or sexual reproduction
• There is competition
• Due to limited resources, the selection pressures favour those better suited to the environment. The fittest produce offspring, which inherit the favourable traits from their parents.
• Over many generations, the frequency of alleles for favourable traits increases and opposite will happen for those with unfavourable traits

Breakdown or summary

So all animals are uniquely different. Some have different coloured fur or different sizes. These animals compete for resources (food) as there is a limited number of resources. Natural selection perssures (e.g. predators/weather (basically things that kill the animals) etc.) will favour those with good traits. Over many generations, the oens with bad traits will die and not have babies to pass these traits off to, so these traits might disappear altogether.

Let’s use an example!

Green birds and Red birds. Green birds are harder to see because they camouflage with the leaves, and so are less likely to be hunted down. The genetic variation is the colour, and the natural selection pressures are the predators that eat the birds. Over time, all the red birds will die out, and the green birds will keep having babies so that they can pass on green coloured alleles to their offspring. Over many generations, green birds will be more commonly found.