Evolution by Natural Selection

Part 1: Darwin

Part 2: Adaptations

Adaptation Song Youtube

http://www.youtube.com/watch?v=YX8VQIJVpTg

Who is Charles Darwin?

Part 1

An English naturalist in the 1800’s– Studied to be a minister

Did most of his research while working on the HMS Beagle as the science officer– Voyage took 5 years

– Sailed along the coast of South America

– Explored the Galapagos Island chain• famous for studying the finches

– Collected thousands of specimens (plants and animals), collected data on weather and ocean currents

How did tortoises and birds differ among the islands of the Galapagos?

Each island had its own type of tortoises and birds that were clearly different from other islands

Darwin’s finches – helped define theory.

 Each bird species evolved from a common finch from the mainland (C. America).

All have different beaks depending on feeding behavior

Phylogeny of the Galapagos Finches

Darwin’s Theory of Evolution

Implications

Another way of saying this is that there is very little gene flow between the islands and the mainland.

Genetic mutations occurred, including beak shape and neck length, which in turn allowed for varied diets.

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Charles Darwin’s TheoryTheory of Evolution by Natural Selection

Theory- well-tested explanation that unifies a broad range ofobservations.Evolution- change in an organism over time; modern organisms descended from ancient organisms

Charles Darwin’s Ideas

Biological evolution is change in species over time.– This was not a new idea at the

time

– But there were no good mechanisms to explain how these changes occurred

Natural selection is the mechanism behind evolution, and this is what Darwin contributed.

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Darwin’s Theory of Natural Selection  Origin of the Species –

book written for both scientists and non-scientists. Created biggest debate of science vs religion ever…

 Survival of the Fittest – theory that only the strongest survive to reproduce and therefore are better adapted to the environment. Basis for theory of evolution.

Proposed The Theory of Evolution By Natural Selection– Based on 5 key observations

• organisms best adapted to the environment will most likely survive; “survival of the fittest”

• organisms that survive will mostly likely reproduce

• genetic traits are passed on from parents to offspring who usually look similar to parents

• more offspring are produced than can survive – the idea of overproduction to ensure some will survive to reproduce

• organisms compete for needed resources:a. foodb. waterc. shelterd. space / territory e. mates 

Artificial selection

Selective Breeding

Selective Breeding– Humans and Dogs– Dogs originated from the Grey Wolf– Breeding for physical traits– Many breeds of dogs - all one species– Human induced and not natural selection

Descent with Modification Each living

species has descended with changes from other species over time

How have humans changed?

Natural Selection and Species Fitness

Overtime, natural selection results in changes in the inherited characteristics of a population.

These changes increase a species fitness (survival rate)

Natural selection does not result in perfection Better adapted to the current circumstances

Darwin’s Theory of Evolution Selective Breeding- humans choose specific organisms for breeding

because they have useful traits from the natural variation within a species, hoping to pass on so these traits accummulate in offspring

Struggle for existence- competition among members of a species for food, living space, and the other necessities of life.

Fitness- ability of an organism to survive and reproduce in its

environment.

Survival of the fittest- individuals that are best suited for their environment survive and reproduce most successfully.

Descent with Modifications- principal that each living species has descended, with changes, from other species over time.

Evidence of Evolution

Fossil Record

Homologous Body structures Vestigial Structures

Similarities in Embryology Geographic Distribution of Living

Species

Relative vs. Absolute Dating

Carbon-14 Dating

Evidence of Evolution

Homologous Body Structures

– A body part that is structurally similar in 2 or more species

e.g. Wing of bat, human arm, leg of turtle

Turtle

Alligator

Bird

Homologous Body Structures

Vestigial Organs

– traces of homologous organs in other species– Organ that serves no useful function

e.g. Appendix

Cormorants of Galapagos

Evidence of Evolution

Similarities in Embryology

– In their early stages of development, chickens, turtles, rats etc. look similar

Embryological development

The development of pesticide resistance in insects is another example of real-time evolutionary change.

Natural selection is also responsible for:

• antibiotic resistance in bacteria

• herbicide resistance of weeds

• HIV resistance to anti- retroviral drugs

What are Adaptations?

Part 2

Types of Adaptations

structural:– a body part or coloration that aids survival

1.) wings, beak shapes, long legs, webbed feet antlers, etc.

2.) camouflage or protective coloration * allows an organism to blend in or

hide in its surroundings

3.) mimicry or protective resemblance * organism looks like or acts like

something it’s not

Physiological– the ability to control life functions to

aid survival

1.) hibernation (slows down metabolism, breathing, heart rate)

2.) marine mammals holding breath for long time

3.) certain plants in extreme conditions (salty, dry, underwater)

Behavioral:– actions that aid survival

learned behaviors1.) behaviors taught to or learned by

experience2.) example: knowing where the water

hole is or knowing what to eat Instincts

1.) behaviors genetically inherited from parents; “just know how”2.) example: knowing when to migrate,

sensing danger, mating season

Traits that help an organism survive – Helpful, positive physical or behavioral

characteristics

Allow organisms to:

1. get food/water

2. protect themselves

3. reproduce/find a mate

4. withstand environment