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, breaking the 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 and is inherited

• Organisms with better traits in environment live

  longer and reproduce

• Gradual change in population =

  favorable characteristics more

  frequent over time

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

process where two or more species influence each other's evolution

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?

an evolutionary theory stating that species remain stable for long periods and then experience rapid bursts of change (punctuated)

• Stephen J Gould hypothesized that evolution is a “standstill” process punctuated by short revolutionary events of rapid evolution

• During these evolution events, species become extinct and are replaced by other wholly new forms

• Supported by the Fossil Record

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.

What hypothesis did Stanley Miller test?

• If early gases are exposed to energy then organic compounds will form

• He used the thinking that complex molecules formed from simple molecules

What did Lamark hypothesize?

Hypothesized that organisms strive to improve themselves and become more advanced

Principle of Use and Disuse from Lamark

Correct: organisms strive to improve themselves to become more evolutionarily advanced to survive in their environment

Incorrect: acquired traits are genetic

• DISPROVEN bc August Wiesmann cut the tails off mice for 22 generations, but the mice continued to produce baby mice with normal tails

Darwin’s Voyage

• Charles Darwin traveled on the Beagle

• Darwin became interested in organisms on the Galapagos Islands

• Darwin published a book based on his idea “descent with modification,” called the Origin of Species

Darwin’s Observations

• Darwin collected 13 different species of finches

• Each finch species had a distinctive beak

• The Galapagos are relatively young

• He hypothesized an original finch (or a few of the same species) had been blown off course from South America

• Offspring of the original finch may have adapted to different environments and food sources

• Over millions of years, large differences could have accumulated to create different species

Fossil

any trace of an organism that lived long ago

Types of fossils

• Some organisms become trapped in ice or amber = VERY REVEALING

• Most are in sand or clay = organism becomes petrified (turned to rock)

What does layering of sedimentary rock tell us?

when organisms existed

What does the fossil record support?

evolution

• Fossils in lower rock layers are older than those in higher layers

What is an argument AGAINST evolution?

the fossil record is incomplete

Comparative Embryology

embryos of related organisms develop in similar ways

Comparative Biochemistry

the structure of hemoglobin in a chimpanzee strongly resembles the structure of hemoglobin in humans

What is common in all life forms?

• Adenine

• Tynine

• Cytosine

• Guanine

How identical is DNA between humans and chimps?

99% identical

How identical is DNA between humans and other mammals?

80% identical

Comparative Anatomy

the comparison of the structure (anatomy) of one animal or plant with the structure of a different animal or plant

Three ways to compare anatomy:

• Homologous structures

• Analogous structures

• Vestigial organs

Homologous Structures

characteristics that are similar because they are inherited by a common ancestor and have similar embryological development

ex. a human arm and a chimp arm

Analogous Structures

features that serve identical functions, and look similar, but have very different embryological development

ex. wings of a bat and a butterfly

Vestigial Organs

inherited structures that may have been useful to an ancestor but have no use nowadays

ex. human tailbone, appendix, wisdom teeth

Rapid evolution

evolution that occurs over a shorter period of time

ex.

• Bacteria builds resistance to antibiotics

• Viruses: AIDS is one of the fastest evolving viruses today

• COVID is quickly evolving

Artificial selection

evolutionary process in which humans consciously select for or against particular features in organisms

ex. dog breeders

What helped lead to the theory of natural selection?

Breeders generated new varieties of plants and animals by selecting parents with desirable traits

Major extinction event

65 million years ago an asteroid collided with earth and the dinosaurs died out

• Mammals went on living because they were nocturnal and reproduced quickly

Causes of extinction

#1 cause = habitat destruction

#2 cause = invasive species

Extinction

termination of a species

Cambrian Explosion

when the first animals appeared → led to a breakthrough in the diversity of LIFE

What is the largest living mammal?

whale

Tree of Life

a model and research tool used to explore the evolution of life and describe the relationships between organisms, both living and extinct

Oxygen Revolution

After photosynthesis evolved, oxygen became available