Intro to Evolution

Evolution

gradual change over time

When the Earth first formed, what type of atmosphere was there?

primitive atmosphere

What did the primitive atmosphere contain?

• Methane gas (CH4)

• Ammonia (NH3)

• Hydrogen (H2)

• Water vapor (H2O)

What released atoms to form simple organic molecules?

UV rays and lightning bombarded the atmosphere and broke bonds in gas molecules

What led to the first heterotrophs?

Membranes formed around organic compounds → lead to the primitive cell that uses anaerobic respiration for energy = first heterotrophs!

Heterotrophs

an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter.

• similar to present day bacteria

What was the result of simple organic molecules used for food being used up?

a competition for food

• cells evolved to make their own food →leading to the first autotrophs

Autotrophs

produce their own food through photosynthesis or chemosynthesis

What happened as a result of photosynthesis evolving?

oxygen would become available/abundant, changing the course of life forever

What did lightning convert?

free O2 to ozone molecules

The ozone layer blocking the UV rays allowed for what?

evolution of new organisms

What is an acquired trait caused by?

It arises during an organism’s lifetime as a result of the organism’s experience or behavior

• NOT CAUSED BY GENES

Summary of Darwinian Evolution

• Overproduction: a production will produce an overabundant number of offspring

• Limited resources → not all offspring will survive

• Variation exists in a population

• Variations are inherited

• Individuals that have the best traits to fit into their environment will live longer and leave more offspring

• Gradual change in a population with favorable characteristics accumulating over generations

Overproduction

a production will produce an overabundant number of offspring

As a result of limited resources, …

not all offspring will survive

What exists in a population?

variation

What is inherited?

variations

Individuals that have the best traits to fit into their environment will…

• live longer

• leave more offspring

What accumulates over generations?

gradual change in a population with favorable characteristics

Where do variations come from?

• Mutations – can be favorable

• Recombination (crossing over) – during meiosis

Natural Selection

the process through which populations of living organisms adapt and change

What type of phenotypes do organisms adapt to?

phenotypes that are favorable to their environment to help improve their fitness

Fitness

the ability for an organism to survive and reproduce in their environment

What is an Example of Natural Selection?

Insecticide Resistance– DDT

• Humans spray crops with insecticide

• Resistant insects survive

• Frequency of resistant insects will grow

Gene Pool

entire collection of genes among a population

Population Genetics

the study of gene pools and the change they undergo

Adaptations

a change or the process of change by which an organism/species becomes better suited to its environment

How are adaptations possible?

due to variations

- the variations may improve or reduce fitness

What types of variations are preserved by natural selection?

variations that aid in survival

What happens when over time, all members have inherited the variation?

it becomes an adaptation

What are the types of adaptations?

• Structural

• Physiological/Behavioral

Structural adaptations

• Woodpeckers tongue is long and narrow to get food out of small openings in trees

Physiological/Behavioral adaptations

• Poison venom of a snake

• Birds migrate in search of food

Species

a group of organisms that can interbreed and produce fertile offspring in nature

• the offspring needs to be fertile in order for it to be considered a species

• ex. female horse + male donkey = mule (sterile). A mule cannot reproduce → it’s not a species

What are the Types of Evolution? (5)

• Convergent evolution

• Divergent evolution

• Coevolution

• Gradualism

• Punctuated equilibrium

Convergent Evolution

2 species evolve similar characteristics due to common environmental conditions, not common ancestry

• ex: wings of bat and bird

• ex: fins of shark and dolphin

Divergent Evolution (aka adaptive radiation):

2 or more species arise from a common ancestor

Can be a result of geographic isolation, driven by particulars of the location

• ex: fox and dogs

• ex: Darwin's finches

Coevolution

The change of two or more species in close association with each other

Ex: predator and prey

What's a specific example of coevolution?

plants and the animals that pollinate them

-Bats with slender, specialized tongues can feed on nectar of certain flowers, picking up pollen as they do

-The flowers coevolved with the bats, (attractive to bats)

-Bats transfer pollen from one flower to another

Gradualism

slow and steady change in a species

What is punctuated equilibrium?

Stephen J Gould hypothesized that evolution is a "standstill" process punctuated by short revolutionary events of rapid evolution, species then become extinct and are replaced by other wholly new forms

Example of punctuated equilibrium

-A cheetah species has no spots. However, due to a gene mutation, a cheetah cub is born with spots.

-Because this adaptation helps the cheetah to hide and survive, more cheetahs are born with spots.