Evolution

People

Evolution
Change in organisms over time
🡪Explains how modern descended from ancient organisms

{{Jean Baptiste Lamarck--{{

French naturalist 1744 - 1829

First to recognize thatorganisms change over time

Theory of Acquired Characteristics

  • Organisms acquire or lose traits during their lifetime.
    • These traits are passed to the offspring

Ex. If a giraffe stretches its neck, increases its length, its children will be born with longer necks.

Theory of Use and Disuse

  • If body part is not used, over time, the ability to use it is lost.
  • If body part is used, it gets stronger and more prominent.

- Use it or lose it.

{{Charles Darwin--{{

Naturalist

Born in England

Journaled observations
Collected specimens
Compared environments: desert, jungle, mountain tops, islands
Asked Questions

Features of organisms fit their environment

{{Influenced by Hutton and Lyell{{Geologists Earth is very old (millions of years) Earth has been formed by geologic forces Earth is under constant geologic forces

{{Thomas Malthus{{

Economist
Studied human population growth
Populations get checked by diseases, famine, war
Overpopulation demands death

{{Alfred Wallace{{

naturalist studying in Malaysia*
Corresponded with Darwin re: Natural Selection by means of Survival of the Fittest

w/ Darwin jointly published a paper of theory of evolution by natural selection August 1858

Darwin published his book “Origin of Species” in 1859 – grabbed public attention

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Earth

The Earth is 4.6 billion years old
All continents were together. This landmass was called Pangaea.
Four eras:
Precambrian
Paleozoic
Mesozoic
Cenozoic

  • Earth is 4.5 billion years old (4,500 million years)
  • Early Earth atmosphere
    • CO2, CO, N2, H2O, hydrogen cyanide, hydrogen sulfide - toxic atmosphere
  • First evidence of life
    • 3.8 billion years ago - Prokaryotic cells (bacteria) are oldest fossils known  (no oxygen yet)
    • 2.2 billion years ago - photosynthetic bacteria started producing O2
    • (product of photosynthesis)
    • 2.0 billion years ago - Eukaryotic cells
    • 700 million  years ago – Invertebrates (no bones)
    • 500 million years ago – Vertebrates (fishes)
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Fossils

Any evidence of an organism that lived long ago. can be complete organisms (plant, animal, fungi, protista, bacteria) parts of organisms footprints eggs seeds pollen droppings (coprolites)

Speciation

Species:
group of organisms that can
- interbreed
and
- produce fertile offspring

Unit of Evolution = Population

  • If a group within a population becomes isolated  🡪 they may change over time.

    • occurs when a subgroup changes so much, they cannot interbreed with original population.

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    • is the first step towards the formation of a new species

Morphology = the study of form and structure of organisms

Direction of evolution-

CONVERGENT ( together/similar)

DIVERGENT (apart)

CAUSES-

Behavioral

Two populations with different courtship behaviors will not interbreed

Different songs (birds) or mating calls (frogs)

Different scents (insects)

Temporal

Basically they reproduce at different times so they cant reproduce together I.E grasshopper 1 mates in spring but grasshopper 2 mates in winter….

Geographic

  • A physical barrier separates (splits) the original population
  • Barriers: Rivers, mountains, bodies of water

How fast is evolution?

H

how fast are changes

how fast is evolution

) Gradualism-   slow small changes

Punctuated Equilibrium –

no change then fast change

Hardy-Weinberg Equilibrium

Hardy-Weinberg Equilibrium

The genetic makeup of an individual is its genotype
(BB, Bb, bb)
A population consists of many genotypes.
All the genotypes in a population make up the gene pool.
For each gene, the gene pool includes all the different alleles (B, b) for that gene in the population.
The frequency (%) of the different alleles (B, b) in the gene pool can be quantified
Allele frequency is how often an allele occurs in a gene pool.

  • Natural Selection
  • Choosing your mates -  known as  Sexual Selection
  • Mutations - changes in the gene code
  • Migration - new individuals bringing or taking aways traits
  • Random events that affect individuals regardless of their fitness - happens in small populations - Genetic Drift

Allele frequencies do not change in a population if :

  1. There is no natural selection   -- all individuals have an equal chance of reproducing and passing their genes to the next generation.
  2. Mating is random  -- individuals do not choose mates based on genotype.
  3. No new mutations occur -- no new alleles are being created.
  4. There is no migration -- no one is moving into or out of the population****.

The population is very large -- minimize the effect of random changes

The Hardy-Weinberg Equilibrium is a tool to evaluate if a population is changing (evolving) or not.

If no reasons, population should not change- frequencies of alleles remain constant if not evolving (changing)