What is evolution? Explain what you

know.

EXPLORING CHANGE OVER TIME

HOW DID ORGANISMS EVOLVE?

Evolution is the change in heritable traits

through generations • CHANGE OVER TIME

• Occurs in populations, not individual organisms

At the time life emerged on earth (about

3.8 billion years ago), the atmosphere is

thought to have contained very little

oxygen! • First cells were thought to be anaerobic

• Recall that “anaerobic” means “without oxygen”

As the atmosphere of the Earth changed,

so did the development of organisms

These prokaryotic (simple), anaerobic

cells were able to exist in Earth’s early

atmosphere

As Earth’s atmosphere and conditions

changed, photosynthetic prokaryotes

evolved, using sunlight to produce food • What molecule do photosynthetic organisms

produce as byproduct (waste)?

Eventually, Earth’s atmosphere became

filled with oxygen • Aerobic organisms evolved

This resulted in the evolution of

eukaryotic complex multicellular

organisms we have on Earth today!

The endosymbiotic theory proposes that

eukaryotic cells arose from living communities

formed by prokaryotic organisms.

~2 billion years ago: • Evolution of internal membranes in prokaryotes The result was the ancestor of all eukaryotic cells.

Endosymbiotic theory: Eukaryotic cells formed from a symbiotic relationship among several different prokaryotic organisms • Prokaryotes that use oxygen to generate energy-rich

molecules of ATP evolved into mitochondria.

• Prokaryotes that carried out photosynthesis evolved into chloroplasts.

Fossils show us the similarities between

organisms of the past and present

220 Million Years Ago 190 Million Years Ago Today

Homologies describe similarities

between the anatomical structures of

species

Vestigial structures are anatomical

structures that still appear, but are no

longer used! • Examples: Tails in humans, legs in snakes

• Suggests that these structures may have existed

at a previous time or in an ancestor; organisms

evolved and structures not needed

Insects and animals often have very similar embryonic development • Ex. All

vertebrates (have a backbone) have similar development

• Suggests a common ancestor

Comparison of DNA and macromolecules

between organisms • Through gel electrophoresis

• Tells us what organisms are closely related

1. Explain how cells are thought to have

evolved over time.

2. What are the different piece of evidence

we have for evolution?

Moth

Bird wing

Type of Evidence?

baby elephant

in womb

1-2 feet long

OSTRICH

EMU

SURVIVAL OF THE FITTEST

Charles Darwin is best known for his contributions to the theory of Evolution

On a five year voyage on a ship called the Beagle, Darwin recorded his observations of organisms and fossils he found along the way

This led Darwin to develop the idea of evolution and natural selection

“Survival of the Fittest” means that those

organisms best adapted to their environment

will survive, reproduce, and pass on genes

• “Fittest” means best adapted, not strongest!

Any heritable trait an organism has that

helps it to survive

What are some adaptations of this falcon?

If an organism does not have adaptations

to best fit its environment, it will die

“Survival of the Fittest” • Example: Bird beaks-Imagine that birds had

different sized beaks in an area where the food

source was seeds. In order to crack them, the

birds needed a large, strong beak. Which would

survive and reproduce?

Species have the potential to increase exponentially, but environmental factors maintain lower population numbers • Resources required to sustain life • Environmental conditions • Relationships among organisms in food web

Changing environments select for specific phenotypes • Those organisms with favorable adaptations survive,

reproduce, and pass on their alleles to future generation

• Over time, the accumulation of favored alleles leads to a change in species (change over time = evolution)

Organisms are constantly changing and adapting; bacteria reproduce and evolve quickly to adapt to constant changes!

Humans often use antibiotics to combat harmful bacteria (ex. Staphylococcus)

Some bacteria are born with a natural resistance (an adaptation!) to the antibiotic

These bacteria will survive and reproduce, creating a group that are resistant to the drugs

Pesticide Resistance in Plants Antivirals Passive Immunity: Immunity to certain

diseases is given from mother to baby at birth • Continued through antibodies passed through

breastmilk Active Immunity: Immunity acquired

through exposure to a disease • After exposure, your body builds up an immunity • Vaccines allow you to artificially gain an active

immunity without exposure to the actual disease

Genetic Recombination • Dominant and Recessive alleles in genes, along

with polygenetic traits and complex genetics,

lead to individual organisms with different

phenotypes (and thus, adaptations)

Mutations • Changes in DNA sequences can introduce both

good and bad new traits into a population

(ex. Immunities, resistant bacteria, pesticide

resistant plants)

What does it mean to be the “fittest” individual?

Which moth has the greatest chance for survival? Why?

Over time as natural selection occurs and the moths that survive go on to reproduce, what color will be most common in the population?

HOW SPECIES CHANGE OVER TIME

Speciation refers to the evolutionary

process by which new biological species

arise

When one extreme phenotype has the

best chance to survive

As a result, the frequency (number) of

those with that phenotype shift over time

Woodpecker beaks

DIRECTIONAL

selection

Using the diagram

as evidence, how did

the horse evolve

over time?

Hypothesize why

these changes could

have happened.

When the intermediate phenotype has

the best chance to survive • Heterozygote

advantage

• Birth weight

When both extreme phenotypes have the

best chance to survive • Peppered moth

Decide if the following scenarios are directional, stabilizing, or disruptive selection. • In a population of green, white, and brown

grasshoppers, the green often survive due to their body color matching the grass. Brown and white are often preyed upon by predators.

• In mollusks, white and black mollusks survive well at different levels of water. Grey mollusks are a target for predators.

• In human babies, small and large babies bring complications at birth. As a result, most babies are born in the 6-8 pound range.

HOW SPECIES CHANGE OVER TIME

When mountains, islands, etc. keep a

population isolated

Species will meet different environmental

challenges, change and evolve independently

than the original population

Lemurs of

Madegascar

Differences in phenotype within one gene • Example: Eye color in humans

• Brown eyes are naturally protected from the sun’s

glare

When one species evolves due to a

specific interaction with another species • Example: Flowers and birds/insects; flowers

pollinated by hummingbirds often have a

narrow, tubular shape

The change in a frequency of a gene variant (allele) in a population due to random chance • Due to a random event, a

significant change happens to the organisms in a population

• Much more frequent is small populations!

• Example: Founder Effect

Bottleneck Effect

1. What is survival of the fittest? How does this fit into the idea of natural selection?

2. What would occur over time if you had a group of organisms who were separated by a river?

3. Sometimes, natural selection does not play out how we expect. What is it called when selection takes place due to random chance?

CLASSIFYING ORGANISMS

Classification systems are how we

organize organisms

This is called taxonomy

The classification of organisms has

changed and evolved over the years due

to new knowledge • Greater understanding of evolutionary

relationships, thanks to DNA technology, has

allowed for more detailed classification

The classification of organisms begins with the largest groupings and moves down to the smallest (domain species)

The classification order is as follows: • Domain

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Easy way to remember: King

Phillip Came Over For

Grandma’s Spaghetti!!!

Group of the same organisms • Live together

• Mate and produce viable offspring

“Viable” means they can have babies of their own

The scientific name of an organism is the

Genus and Species of an organism • Always written in italics

• Example: Humans are Homo Sapians

Only species are able to interbreed!

Only species are able to interbreed. Organisms of two different species normally will not breed

Sometimes, organisms within the same genus are able to interbreed, but the offspring are not viable (they cannot reproduce!) • Example: Mules; Ligers

• These hybrid organisms are much more common in captivity than in the wild

1. What is the scientific name for

humans?

2. What components make up the

scientific name?

3. What classifies a species?

A key that helps identify an organism

Uses questions to lead you to the

scientific name of an organism • By looking at features of an organism, the key

will help you determine what it is!

1. Organisms are classified into 7 major groups. List these groups in order from largest to smallest.

2. Which is the best description of how natural selection changes a species over time?

a) Survival of the strongest organisms in an environment

b) Elimination of the smallest organisms by largest organisms

c) Survival of the organisms genetically best adapted to the environment

d) Survival of the organisms that occupy the largest area in an environment

Shows the evolutionary relationship between

organisms

Can show which organisms are more closely

related than other organisms

Which organism is

more closely related

to man? __________

Which organism is

man more closely

related to: Frog or

bird? Why?

Shows relationships up-close;

characteristics they share

1. Which two organisms are most closely

related?

2. What trait do lizards have that salamanders

don’t?

A. Evolution is survival of the smartest

B. Evolution is survival of the strongest

C. Evolution is survival of the fittest

D. Evolution is survival by luck

The forelimbs of whales, dogs, humans,

and bats are all similar in their

arrangement and structure. What

category of evidence is exemplified? a) Fossils

b) anatomical similarities

c) biochemical comparison

d) embryological comparison

a) Organs

b) Adaptations

c) Natural Selection

d) Vestigial Structures

a) It doesn’t exist

b) It can reproduce and have offspring

c) It’s parents are not the same

d) It cannot reproduce and have babies of

its own

a) Variation

b) Natural Selection

c) Isolation

d) Speciation

How does pesticide resistance in insects lead to the evolution of the overall insect species? a) The species will develop different eating methods

to avoid the pesticides

b) Insects surviving pesticide applications become weaker and will eventually die

c) Farmers will use different pesticides to kill the insects, eliminating the species

d) Pesticide-resistant insects will survive and reproduce, increasing the percentage of pesticide-resistant insects in the population

Which immune response is passed from

mother to child through breast feeding? a) Active

b) Passive

c) Humoral

d) Cell-mediated

Natural selection cannot occur without

a) competition for unlimited resources.

b) gradual warming of Earth.

c) genetic variation in species.

d) asexual reproduction in species.

The classification of some organisms has changed. Which new process is used to reclassify organisms? a) Organisms are now given Latin-based

scientific names

b) Structures are now examined at the molecular level

c) Organisms are now divided into three kingdoms

d) Structures are now used to classify organisms

Define the following terms: • Fitness

• Natural Selection

• Speciation

• Genetic Drift

• Species

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You have a test today! Take 10 minutes to study: • Evidence of Evolution

• Darwin’s Theory of Evolution

• Types of Selection

• Speciation

• Dichotomous Keys

• Phylogenetic Trees

• Classification: REMEMBER-King Phillip Came Over For Grandma’s Spaghetti!