EVOLUTION. Origins of life -Earth formed about 4.6 billion years ago -Early Earth had many active volcanoes. -These volcanoes released: 1. water vapor,

EVOLUTION

Origins of life

-Earth formed about 4.6 billion years ago

-Early Earth had many active volcanoes.

-These volcanoes released:

1. water vapor, which eventually led to formation of oceans

2. Gases, such as: methane, hydrogen, nitrogen, ammonia, carbon dioxide, and carbon monoxide

-Earth’s early atmosphere had little to no oxygen.

Miller-Urey Experiments◦Showed that organic molelcules, specifically, polypeptides (which are chains of amino acids) could be formed from elements present on Early Earth

◦These organic molecules of polypeptides could join together to create life

What were the first living organisms on Earth?◦Fossil records show that the first living organisms appeared about 3.5 billion years ago and were simple, single-celled organisms.

◦The sequence of development is as follows:

Anaerobic prokaryotes photosynthetic prokaryotes unicellular eukaryotes multicellular eukaryotes

*anaerobic means no oxygen is required

Where did oxygen first come from?◦Most likely from photosynthetic bacteria, such as cyanobacteria

Anaerobic prokaryotes photosynthetic prokaryotes unicellular eukaryotes multicellular eukaryotes

Where did oxygen first come from?◦Most likely from photosynthetic bacteria, such as cyanobacteria

Anaerobic prokaryotes photosynthetic prokaryotes unicellular eukaryotes multicellular eukaryotes

Review: What is the formula for photosynthesis?

Evolution

Question to think about: Do humans ‘come from’ monkeys?

By the end of this Evolution unit, you will be able to answer this question correctly as a scientist!

Evolution

Definition: a change in the genetic composition of a population of organisms over time.

Summary: change inorganisms over time.

Evolution

You may also see this definition:

Descent with modification from common ancestors

How does evolution occur?◦First hypothesis, which was incorrect (i.e. unsupported, was proposed by Jean-Baptiste Lamarck in 1809

◦Theory of acquired traits: physiological changes that an organisms acquires throughout its lifetime may be passed onto offspring

◦This idea was good in that it was a hypothesis on how evolution occurred, but it was bad in that there is no evidence to support it.

Theory of acquired traits: not a supported hypothesis for evolution

Hypothesis: Actual results

Darwin’s Theory of Natural Selection

◦English naturalist

◦Sailed on the HMS Beagle in 1831to make natural history collections

◦His observations led to the theory of evolution by natural selection

◦Wrote a book titled, On the Origin of Species

Review: define evolution

a. an adaptation of an organism to its environment

b. a sudden replacement of one community by another

c. a geographic or reproductive isolation of organisms

d. a process of change in organisms over a period of time

Review: define evolution

a. an adaptation of an organism to its environment

b. a sudden replacement of one community by another

c. a geographic or reproductive isolation of organisms

d. a process of change in organisms over a period of time

Review: Which statement would most likely be in agreement with Lamarck’s theory of evolution?

a. Black moths have evolved in an area because they were better adapted to the environment and had high rates of survival

and reproduction.

b. Geographic barriers may lead to reproductive isolation and the production of new species.

c. Giraffes have long necks because their ancestors stretched their necks reaching for food, and this trait was passed on to their offspring.

d. Most variations in animals and plants are due to random chromosomal and gene mutation.

Review: Which statement would most likely be in agreement with Lamarck’s theory of evolution?

a. Black moths have evolved in an area because they were better adapted to the environment and had high rates of survival

and reproduction.

b. Geographic barriers may lead to reproductive isolation and the production of new species.

c. Giraffes have long necks because their ancestors stretched their necks reaching for food, and this trait was passed on to their offspring.

d. Most variations in animals and plants are due to random chromosomal and gene mutation.

Evolution by natural selection

Definition: a primary mechanism of evolution in which organisms with favorable traits are more likely to reproduce

Summary: main process for evolution to occur

Components of natural selection

1. There are not enough resources (such as food) for all individuals in a population

2. There is variation of traits among individuals

3. These traits are heritable

4. Individuals with the ‘better’ trait will survive longer and reproduce more than those without the ‘better’ trait.

Important vocabulary wordsFitness: an organism’s relative ability to survive and produce fertile offspring.Adaptation: feature that improves fitness. Example: camouflage

Guided Practice: beetles1. There are lots of beetles, more than

the environment can support

2. The beetles vary in color. Some are green, and some are orange.

3. The colors are inherited from parents.

4. Birds like to eat green beetles. So, being an orange color is a better trait because they are not eaten. Orange beetles are better at surviving and reproducing (have higher fitness)

Being orange is an adaptation!

Guided Practice: beetles1. Did evolution occur? Why or why not?

2. How did evolution occur?

Guided Practice: beetles1. Did evolution occur? Why or why not?

Yes, because there was change in the population over time. The beetles were both green and orange in the beginning, but at the end, all beetles are orange.

2. How did evolution occur?

Through natural selection. The orange beetles were better at surviving and reproducing.

Explain how giraffes evolved to have longer necks: Think-pair-share 5 minutes

Things to think about in your answer:

1. Should there be more or fewer individuals in a population than an environment can support? What resources do giraffes need to survive?

2. Is there variation in neck length amongst the giraffes in the population, or are they all the same?

3. Is neck length heritable or is determined by the environment?

4. Are certain giraffes better at surviving and reproducing than others? Why or why not?

Other mechanisms of evolution

1. Natural selection

2. Mutations

3. Genetic drift

4. Gene Flow

5. Nonrandom mating

Mutation

Change in genetic information

Mutations that occur in gametes (sperm and eggs) are passed onto offspring

May contribute to genetic variation

Genetic DriftWhen genetic composition changes by chance

More noticeable in smaller populations

Gene flow

Immigration or emigration of individuals

Nonrandom mating

Selective mating based on preferences

Phylogenetic trees

Hypotheses for the evolutionary relatedness of organisms

Cladograms

◦Diagrams used to show how organisms are related by descent from common ancestors

How to read a cladogram

◦Organisms that are closer to each other share a more recent common ancestor

◦Example: a chimp is more closely related to a mouse than a pigeon because the chimp & mouse share a more recent common ancestor

How to read a cladogram practice:◦Is the lizard more closely related to a salamander or a hagfish?

Evidences for evolution

1.Molecular

2.Anatomy

3.Vestigial structures

4.Comparative embryology

5.Fossils

Evidences for Evolution: Molecular1. All organisms have the same 20 amino acids that make up proteins

2. All organisms use ATP

3. Organisms that share similar traits also show similar DNA base sequences

-Comparing DNA sequences is one of the best ways to understand evolutionary relationships

Evidences for Evolution: Anatomy◦Homologous structures: structures among organisms that are similar structurally, but different in function.

◦Due to inheritance from a recent common ancestor

Evidences for Evolution: Anatomy

◦Analagous structures: structures among organisms that are different structurally, but appear and function similarly.

◦These occur when the organisms live similar life styles, not because of sharing a recent common ancestor

Evidences for Evolution: Vestigial structures◦Structures that lost most or all of their ancestral function, but have been retained through evolution.

◦Examples:

Vestigial Structures Example:◦ Pelvic bones in whales

◦Whales don’t walk. So, why do they need

pelvic bones?!?!?!

Answer: These pelvic bones have been reduced

and are not used. This vestigial structure

suggests inheritance from a recent common ancestor

Vestigial Structures Example:

◦ Pelvic bones in whales

◦Whales don’t walk. So, why do they need

pelvic bones?!?!?!

Answer: These pelvic bones have been reduced

and are not used. This vestigial structure

suggests inheritance from a recent common ancestor

Did you know that: whales are mammals??

Vestigial structure example:

Human embryos have tails, which later moves into the body, but retains much of its bone structure in the coccyx

Evidences for Evolution: Comparative Embryology◦Embryos of animals with backbones (vertebrates) look very similar

◦This indicates that the rules of embryonic development are similar among vertebrates, meaning that all vertebrates share a common ancestor

Evidence for Evolution: Fossils-Fossils are preserved remains of animals, plants, and other organisms.

-When fossils are arranged according to age, a progressive series of changes (i.e. evolution) can be observed

Stop and jot: 4 minutes

In your notes, list and explain four evidences of evolution.

Speciation

◦Speciation is a process by which species evolve

◦A species is a group of organisms that can interbreed and produce fertile offspring

◦How do species form?1. Geographic isolation2. Behavioral isolation

Geographic isolation◦Populations separated by geographic barriers (rivers, mountains, bodies of water, etc.)

◦Doesn’t always lead to new species.

Behavioral isolation• Capable of interbreeding, but have different courtship rituals.

Patterns of evolution

1.Adaptive radiation

2.Convergent evolution

3.Coevolution

Patterns of Evolution

Adaptive Radiation

◦Small group of species evolve into different forms that live in different ways.

Patterns of EvolutionConvergent Evolution

◦Unrelated organisms begin to resemble each other.◦Similar environmental demands. Produces analagous structures

Patterns of Evolution

Coevolution

◦Two species evolve in response to changes in each other.

Evolution over a larger time scale

1.Punctuated equilibrium: periods of quick evolution followed by periods of stasis.

2.Gradualism: evolution that occurs gradually, or slowly over time.

Evolution

Question to think about: Do humans ‘come from’ monkeys?

By the end of this Evolution unit, you will be able to answer this question correctly as a scientist!

Answer:◦No, humans do not ‘come from’

monkeys.

◦Humans and apes (chimpanzees & gorillas) do share genetic similarities, and thus, we share a recent common ancestor!◦Examples: large brains relative to

body size, relatively long childhood, intelligence (reasoning, sense of self), and more.

Classification

https://www.youtube.com/watch?v=F38BmgPcZ_I

Crash course video & worksheet