2026-05-16 14:20

Status: #new

Tags: #biology #developing #evolution

Intro to Evolution

Defining evolution

Microevolution

• Small changes over a small period of time for a population
• Any changes does not result in divergence of new species
• Microevolutionary changes occur within a population

Macroevolution

• Large changes over a larger period of time for a population
• Can result in speciation or the emergence of new species
• Speciation - The evolutionary process by which populations evolve to create new species

Evolution

• Is the process of change over time for a population AND involves processes of genetic inheritance

Variation and Adaptation

Variation

• Natural differences between individual organisms, which are DNA dependent.
• Can have three possible effects
  • 1. Positive - Increases organisms chances of survival and reproduction
  • 2. Negative - Decreases organisms chances of survival and reproduction
  • 3. No change - Has no effect on survival or reproduction

Adaptations

• Adaptations are developed through gradual accumulative changes. Crucially they are not chosen by the organisms
• Instead, they are random heritable changes in DNA that accumulate over many generations - (Beneficial changes are those which remain to allow for reproduction)
• An organism is said to be thriving when it can resist Selective pressures and procreate

Defining Adaptations

• Thus adaptations are modes which organisms use for survival in their environment.
  • Must begin with variation. Not all variation leads to adaptation however.
• Sometimes mutations increase variation within a population
  • Not all mutations can be passed on
  • Mutations can be Positive, Negative or have No change

Mutations and Variations...

• Mutations - Change in DNA sequence of an organism
• Variation - Differences of traits among individuals in a population

Selective Advantage

• A genetic advantage that improves the ability of an organism to survive an environmental change.
  • ie. Lizards in the Galapagos got better at surviving hurricanes, as those with larger fingers were more likely to survive, and procreate, causing their alleles to make up more and more of the gene pool.

Antibiotic Resistance

• Rapid Reproduction and Selection advantage. The idea that after selection occurs, more and more of the gene pool have the resistant traits.

Hardy-Weinberg

Hardy-Weinberg Principle

• If a population does not undergo evolution then the allele frequency is expected to remain constant

Hardy-Weinberg Calculations

p = Frequency of the dominant allele (% in Decimals)
q = Frequency of the recessive allele
p + q = 1
0 < p,q < 1
${\mathrm{p}}^2+2pq+q^2=1$
$p^2$: homozygous dominant individual percentage
$2pq$: heterozygous individual percentage
$q^2$: homozygous recessive individual percentage

Restrictions for Hardy-Weinberg to be valid

• Large population
• Equal mating opportunities
• No mutations occur
• No migrations occur
• No natural selections happen (all individuals can reproduce)

References

5.0 Intro to Evolution
5.1 Natural and Artificial Selection
5.4 Modes of Evolution