Evolution by Evolution by Natural Selection

Evolution by Evolution by Natural Selection

Change over timeChange over time

What is evolution by

natural selection?

What is evolution by

natural selection?Adaptations will spread throughout a

population (species) if:

It helps an organism GET FOOD It helps an organism AVOID PREDATION If helps an organism ATTRACT A MATE

Adaptations will spread throughout a population (species) if:

It helps an organism GET FOOD It helps an organism AVOID PREDATION If helps an organism ATTRACT A MATE

How does How does NATURAL NATURAL SELECTION WORK?SELECTION WORK?How does How does NATURAL NATURAL SELECTION WORK?SELECTION WORK?

VARIATIONSVARIATIONS (don’t help survival, just (don’t help survival, just provide differences among provide differences among organisms) organisms) exist in a populationexist in a population

Ex: Eye color: does it help you…Ex: Eye color: does it help you… GET FOOD?GET FOOD? AVOID PREDATION?AVOID PREDATION? ATTRACT A MATE?ATTRACT A MATE?

VARIATIONSVARIATIONS (don’t help survival, just (don’t help survival, just provide differences among provide differences among organisms) organisms) exist in a populationexist in a population

Ex: Eye color: does it help you…Ex: Eye color: does it help you… GET FOOD?GET FOOD? AVOID PREDATION?AVOID PREDATION? ATTRACT A MATE?ATTRACT A MATE?

How does How does NATURAL NATURAL SELECTION WORK?SELECTION WORK?How does How does NATURAL NATURAL SELECTION WORK?SELECTION WORK?

Adaptations:Adaptations: These traits do These traits do help you survivehelp you survive

Examples: A peacock’s bright Examples: A peacock’s bright colors, red cardinals, a rattle colors, red cardinals, a rattle snake’s rattle, a turtle’s snake’s rattle, a turtle’s shell……what else?shell……what else?

Adaptations:Adaptations: These traits do These traits do help you survivehelp you survive

Examples: A peacock’s bright Examples: A peacock’s bright colors, red cardinals, a rattle colors, red cardinals, a rattle snake’s rattle, a turtle’s snake’s rattle, a turtle’s shell……what else?shell……what else?

NATURAL SELECTION IS A THEORY

What is a theory?

NATURAL SELECTION IS A THEORY

What is a theory? A theory is a well supported testable

explanation of phenomena that have occurred in the natural world

Some common theories include:GravityHeliocentric theory (earth revolves around the Sun)

A theory is a well supported testable explanation of phenomena that have occurred in the natural world

Some common theories include:GravityHeliocentric theory (earth revolves around the Sun)

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Galapagos Islands, Galapagos Islands, EcuadorEcuador

Darwin’s ObservationsDarwin’s Observations

Was fascinated at how WELL ADAPTED the animals were to the island

Noticed that many of the animals he saw on the island closely resembled the animals on the main land but were a BIT DIFFERENT!

Was fascinated at how WELL ADAPTED the animals were to the island

Noticed that many of the animals he saw on the island closely resembled the animals on the main land but were a BIT DIFFERENT!

Darwin’s FinchesDarwin’s FinchesDarwin’s FinchesDarwin’s Finches

Natural SelectionNatural Selection The struggle for existence The struggle for existence =

survival of the fittest Fitness = ability to survive

and reproduce; the result of adaptations Members of the same species

compete for food, living space, and mates

Those that are faster or better camouflaged, etc are more likely to survive…sometimes leading to new traits!

The struggle for existence The struggle for existence = survival of the fittest

Fitness = ability to survive and reproduce; the result of adaptations Members of the same species

compete for food, living space, and mates

Those that are faster or better camouflaged, etc are more likely to survive…sometimes leading to new traits!

Darwin’s Theory of Natural Selection

Darwin’s Theory of Natural Selection

1.1. Overproduction: Overproduction: more offspring are produced than can survive to

maturity

2.2. Genetic variation: Genetic variation: No 2 organisms are exactly alike (so when competition

exists, some may win!).

3.3. Struggle to survive:Struggle to survive: Organism BEST ADAPTED to the new environmental

pressures will survive to REPRODUCE (and pass on adaptation to offspring)

4.4. Differential reproduction:Differential reproduction: In time….. (millions of years)….. the traits in a population

will change (and may form new species).

1.1. Overproduction: Overproduction: more offspring are produced than can survive to

maturity

2.2. Genetic variation: Genetic variation: No 2 organisms are exactly alike (so when competition

exists, some may win!).

3.3. Struggle to survive:Struggle to survive: Organism BEST ADAPTED to the new environmental

pressures will survive to REPRODUCE (and pass on adaptation to offspring)

4.4. Differential reproduction:Differential reproduction: In time….. (millions of years)….. the traits in a population

will change (and may form new species).

Evidence: The Fossil RecordEvidence: The Fossil RecordEvidence: The Fossil RecordEvidence: The Fossil Record Fossils are the Fossils are the

remains of once remains of once living organismsliving organisms

Many different Many different species were species were present on this present on this planet in the past planet in the past

Fossils are the Fossils are the remains of once remains of once living organismsliving organisms

Many different Many different species were species were present on this present on this planet in the past planet in the past

a)a) Ancient sea scorpion Ancient sea scorpion Jaekelopterus Jaekelopterus rhenaniae rhenaniae

b)b) Trilobite Trilobite Isotelus rex Isotelus rex c)c) Dragonfly Dragonfly Meganeura Meganeura

monyi monyi d)d) Millipede Millipede

Arthropleura armataArthropleura armatae)e) Reconstruction of a Reconstruction of a

fossil claw from the fossil claw from the ancient sea scorpion ancient sea scorpion (390 mya)(390 mya)

Comparative sizes of a Comparative sizes of a human male with human male with aquatic creatures that aquatic creatures that existed between 460 existed between 460 and 255 mya:and 255 mya:

SuperpositionSuperposition If no major disturbance has occurred, a If no major disturbance has occurred, a

layer of rock at one place was formed after layer of rock at one place was formed after the layer below itthe layer below it

Provides Provides relative age relative age of fossilof fossil Observe life forms change over timeObserve life forms change over time

SuperpositionSuperposition If no major disturbance has occurred, a If no major disturbance has occurred, a

layer of rock at one place was formed after layer of rock at one place was formed after the layer below itthe layer below it

Provides Provides relative age relative age of fossilof fossil Observe life forms change over timeObserve life forms change over time

Evidence: The Fossil RecordEvidence: The Fossil RecordEvidence: The Fossil RecordEvidence: The Fossil Record

Homologous = similar Homologous = similar anatomical structures anatomical structures in different speciesin different species

Ex: Forearms of a Ex: Forearms of a human, cat, whale, human, cat, whale, and bat are similar in and bat are similar in structure. structure.

Indicates that these Indicates that these organisms shared a organisms shared a common ancestor.common ancestor.

Homologous = similar Homologous = similar anatomical structures anatomical structures in different speciesin different species

Ex: Forearms of a Ex: Forearms of a human, cat, whale, human, cat, whale, and bat are similar in and bat are similar in structure. structure.

Indicates that these Indicates that these organisms shared a organisms shared a common ancestor.common ancestor.

Evidence: Homologous Evidence: Homologous StructuresStructuresEvidence: Homologous Evidence: Homologous StructuresStructures

Analogous = anatomical structures that Analogous = anatomical structures that serve a similar purpose, but are different in serve a similar purpose, but are different in structure.structure. Ex: The wings of a bat and a bird are not similar

in structure but are both meant for flying.

Species with analogous structures doSpecies with analogous structures do NOT NOT share a common ancestor. share a common ancestor. Just adapted to a similar environment

(convergent evolution).

Analogous = anatomical structures that Analogous = anatomical structures that serve a similar purpose, but are different in serve a similar purpose, but are different in structure.structure. Ex: The wings of a bat and a bird are not similar

in structure but are both meant for flying.

Species with analogous structures doSpecies with analogous structures do NOT NOT share a common ancestor. share a common ancestor. Just adapted to a similar environment

(convergent evolution).

Evidence: Analogous StructuresEvidence: Analogous StructuresEvidence: Analogous StructuresEvidence: Analogous Structures

Vestigial = Organs that are no Vestigial = Organs that are no longer useful to the organismlonger useful to the organism Humans: coccyx, wisdom teeth, eye

fold Eyes on the naked mole rat Were present and used in the past

and have since become useless. Not considered vestigial anymore:

appendix

Vestigial = Organs that are no Vestigial = Organs that are no longer useful to the organismlonger useful to the organism Humans: coccyx, wisdom teeth, eye

fold Eyes on the naked mole rat Were present and used in the past

and have since become useless. Not considered vestigial anymore:

appendix

Evidence: Vestigial OrgansEvidence: Vestigial OrgansEvidence: Vestigial OrgansEvidence: Vestigial Organs

Vertebrates all have similar structures in Vertebrates all have similar structures in the early developmental stagesthe early developmental stages Ex: Gill slitsEx: Gill slits

Shows the similarities of the different Shows the similarities of the different vertebrates; suggests common ancestorvertebrates; suggests common ancestor

Vertebrates all have similar structures in Vertebrates all have similar structures in the early developmental stagesthe early developmental stages Ex: Gill slitsEx: Gill slits

Shows the similarities of the different Shows the similarities of the different vertebrates; suggests common ancestorvertebrates; suggests common ancestor

Evidence: EmbryologyEvidence: EmbryologyEvidence: EmbryologyEvidence: Embryology

By comparing the By comparing the DNA, RNA, & DNA, RNA, & ProteinsProteins of organisms scientists of organisms scientists can quantify how alike or can quantify how alike or different two organisms are.different two organisms are.

There is a high level of similarity There is a high level of similarity among all organisms.among all organisms.

Can you believe it??? All life on Can you believe it??? All life on this planet is over 90% the same this planet is over 90% the same when viewed at the DNA levelwhen viewed at the DNA level

By comparing the By comparing the DNA, RNA, & DNA, RNA, & ProteinsProteins of organisms scientists of organisms scientists can quantify how alike or can quantify how alike or different two organisms are.different two organisms are.

There is a high level of similarity There is a high level of similarity among all organisms.among all organisms.

Can you believe it??? All life on Can you believe it??? All life on this planet is over 90% the same this planet is over 90% the same when viewed at the DNA levelwhen viewed at the DNA level

Evidence: Biochemical EvidenceEvidence: Biochemical EvidenceEvidence: Biochemical EvidenceEvidence: Biochemical Evidence