BIO 110 - Darwinism

What is evolution?

• Change over time

• Various processes that transformed ancestral life forms into many species existing today

What is organic evolution?

Change of organisms over time

Age of the solar system

10-20 billion years old

Age of the earth

4.5-5 billion years old

When did life appear?

4 billion years ago

Spontaneous generation?

Idea that organisms could “spring” from non-living material. (Not true)

Domestication of dogz

14,000 years ago artificial selection began by humans choosing desired traits and putting it into that organism

Results of artificial selection

Extreme sizes (Great Dane = big, Chihuahua = small)

Extreme form (Dachshunds=short leg, English bulldog= short snout, hard to breathe)

Homology

Similarity in structure between different species, parts of an organism, or between the different parts of a single organism, often attributable to common ancestry.

Comparative Morphology

Animals like whales + bats have similar bones in forelimbs

Who was George Cuvier?

States that a higher being (God) created the organisms today + multiple catastrophes killed them.

Explanation of dinosaurs

Who was Jean Lamarck?

Animals inherited acquired characteristics.

Was not born w/ a trait but passed on to offspring.

When environments changed organisms changed behavior to survive.

Ex. Giraffe stretching neck w/ nervous fluid to eat leaves.

Offspring inherits it + neck neck continues to stretch

Charles Darwinnn

Born Feb, 12, 1809 in Shrewsbury England.

British naturalist famous for theories + evolution + natural selection

Star pupil of John Henslow (botanist)

What happened on Darwin’s Voyage?

(1831-1836) - Naturalist on the HMS Beagle on British science expedition around the world.

• South America - Found fossils of extinct animals similar to modern species

• Galapagos Islands - noticed many variations among plants+animals of the same type as those in South America. Formed the theory of evolution.

What is the Galapagos Islands?

Volcanic islands far off coast of Ecuador.

All creatures descended from species that arrived on islands elsewhere

Galapagos finches and Darwin

Darwin observed these animals w/ various lifestyles + body forms

When he returned - there were 13 species

This helped him create the theory of natural selection

What is Darwin’s main theory?

Population can change over time when individuals differ in one or more heritable traits responsible for differences in ability to survive+reproduce

What are Darwins theories?

Evolution is real.

Evolution was gradual

Primary mechanism for evolution was natural selection

Millions of species alive today came from 1 original life form through branching process(speciation)

What is Natural selection?

Differential survival + reproduction of classes of organisms that differ from one another in one or more usually heritable characteristics.

• Never due to chance

• Animals that best adapted to their environment

Malthus- Struggle to survive

• Darwins inspiration

• Thomas Malthus = Argued that as population size increases, resource decrease.

• Struggle to live intensifies + conflict increases.

The point of Darwin’s work

Biological evolution doesn’t change individuals.

• Changes entire population

• Traits in population vary among individuals

• Evolution is change in frequency of traits

• Individual of species does not evolve - population of species evolved

Why was Darwin afraid?

The theories he wrote were not published because the Anglican Church could be offended.

Until Alfred Russel Wallace came up w/ the same theories. He forced this man to publish his theory to gain credit.

Alfred R. Wallace

Naturalist who had the same ideas as Darwin

Prompted Darwin to publish his theories in formal paper to gain credit before him.

What is evolutionary selection?

•  variation within species occurs randomly + survival or extinction of each organism is determined by organism’s ability to adapt to environment.

• Organisms adapt w/ traits they already have

What is adaptation 💩

• Any heritable characteristic of organism improving its ability to survive + reproduce in its environment

• Used to describe process of genetic change in population, influenced by natural selection

What is “On the Origin of the Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life” ?

(1859), A book where Darwin put his theories.

After OOS was published Darwin continued to write botany, geology + zoology

Was Darwin’s work still controversial to others?

Many did not like the idea that monkey’s were their ancestor.

What is the Gene Pool?

• All of the genes in the population

• Genetic resource that is shared (in theory) by all members of population

Variation in Phenotypes

• Each kind of gene in gene pool may have two or more alleles

• Individuals inherit different allele combinations

• This leads to variation in phenotype

Types of Gene Mutations

1. Lethal mutation - lead to death 

2. Neutral mutations - no benefit/harm

3. Advantageous mutations - these are beneficial to the organism 

Natural selection is the…

• Difference in the survival and reproductive success of different phenotypes

• Acts directly on phenotypes and indirectly on genotypes

What are the 4 basic ideas that form the theory?

• Organisms can produce large #s of offspring

• Offspring are variable in appearance and function, some of this variation is heritable

• Competition plays a role in which individuals survive

• Survival and reproduction of individuals is not random

What is survival of the fittest?

Whoever creates the most offspring or produces the most.

What comes out of Natural selection?

• A shift in the range of values for a given trait in some direction (directional)

• Stabilization of an existing range of values

• Disruption of an existing range of values 

What is Directional Selection?

• Allele frequencies shift in one direction

Ex. The extreme right version if the species survives to reproduce 

Peppered Moths, an example of directional selection?

• Prior to industrial revolution in England, most common phenotype of this organism was light colored

• After industrial revolution, dark phenotype became more common

Peppered moths

1800s, both colors were common.

Once factories created soot from burning coal the trees were covered.

The lighter organism were eaten by birds while the darker organism blended into the soot

What is Antibiotic Resistance?

• Another Ex. of Directional Selection 

• First came into use in the 1940s

• Overuse has led to selection of an increase in forms of bacteria

• Most susceptible bacteria died out and were replaced by resistant forms

What is stabilizing selection?

• Another type of selection

• Intermediate forms are favored and extremes are eliminated 

• Middle form of species survives

The selection for Gall size

• This organism has 2 major predators

• Wasps preyed on larvae in small ones

• Birds eat larvae in large ones

• The organism that caused medium sized larvae had the highest fitness

Disruptive (Destabilizing) Selection

• Forms at both ends of the range of variation are favored 

• Intermediate forms are selected against 

• Outer forms of the species survive

Disruptive Selction

• In disruptive selection, extremes of visible characteristics or traits (phenotypes) enjoy a greater reproductive success than do intermediate characteristics or traits.

  • Ex. Pseudacraea eurytus (African butterfly)

Pseudacraea eurytus (butterfly) come in three colors 

• There are yellow, orange and red forms & all are the same species 

• All are un-edible for birds so they are not hunted by birds

• BUT the middle colored (Orange) look like a different species so the birds accidentally eat them

• Birds will mistakenly kill the Orange ones hence this is disruptive selection.

Sexual Selection

• Another form of selection

• Selection favors certain secondary sexual characteristics 

• Like feathers or puffy chest in woodcocks 

• Through nonrandom mating, alleles for preferred traits increase since they are chosen as mates more frequently 

What is Gene Flow?

• Physical flow of alleles into a population 

• Tends to keep the gene pools of populations similar

• Counters the differences that result from mutation, natural selection, and genetic drift

What is Bottleneck?

• A severe reduction in population size

• Causes pronounced drift

  Example:

  • Elephant seal population hunted down to just 20 individuals 

  • Population rebounded to 30,000

  • Electrophoresis revealed there is now no allele variation at 24 genes

What is the founder effect?

• When a small # of individuals starts a new population 

• By chance, allele frequencies of founders may not be same as those in original population 

• Effect is pronounced on isolated islands

What is inbreeding?

• Nonrandom mating between related individuals 

• Leads to increased homozygosity

• Can lower fitness when deleterious recessive alleles are expressed

• Amish, cheetahs are a population w/ this