Evolution

Diversity of LifeEvolution - Change over timeTheory - a well supported

testable explanation of phenomena that has occurred in the natural world.

History of Evolution

1795- Hutton published a detailed theory about geological forces that shaped the Earth.

1798- Malthus predicts the human population will grow faster than the space and food supply can sustain it.

1809- Lamarck publishes his theory of the inheritance of acquired traits. Use or disuse.

1833 - Lyell explained processes occurring now have shaped Earth’s geological features over long periods of time.

1831 - Charles Darwin sets sail on the H.M.S. Beagle from England for a voyage around the world.

1836 - Returns to England with many specimens

1859- Darwin publishes On the Origin of Species. He proposed the mechanism for evolution which he called natural selection.

The word “evolution” is not used in The Origin of Species, however Darwin refers to descent with modification, which is descent with changes from other species over time.

Evolution by Natural Selection1. Struggle for Existence – members of each species compete regularly for food, living space, and other requirements for life.–Ex. Predators are fast or have a particular way of ensnaring prey; may be camouflaged or have protection (porcupine)

2.Survival of the Fittesta.Fitness – ability of an

individual to survive and reproduce in its specific environment

Let’s Practice

•Read the cartoon and then answer the questions that follow.

Discussion Questions• When it comes to crickets, what does fitness

mean?

• Is calling good or bad for a cricket's fitness?

• Give some examples of selection at work in this cricket story.

• How does selection favor calling? How does selection favor not calling?

b. Adaptation – inherited characteristic that increases an organism’s chance of survival1. Mimicry

2. Camouflage

3. Warning Color

4. Ability to carry out photosynthesis

5. Hunting methods – in groups or as individuals

Can you find the mantis?

3. Descent with Modification –a. over long periods of time, natural

selection produces organisms that have different structures, establish different niches or occupy different habitats causing species of today to

look different from their ancestors.

b. This implies that all living organisms are related to one another or have common ancestors – common descent

Let’s Practice

•Lab – What Does Adaptation Mean?

• Fossil Record• Homologous Body Structures• Vestigial Organs• Similarities in Early

Development• Molecular Biology

Paleontologists - scientists who study fossils

Preserved remains or evidence of an ancient

organism.

Relative dating - the age of a fossil is determined by comparing its placement with that of fossils in other layers of rock.

See activity on fossils

Radioactive Dating-is the use of half-lives to determine the age of the sample

See activity on fossils

Half-lifelength of time required for half of the radioactive atoms in a sample to decay.See half-life problem

Let’s Practice

•Examine the fossils provided in your notes and answer the questions that follow.

Homologous Body Structuresstructures that have different mature forms in different organisms but develop from the same embryonic material

See activity

Let’s Practice: Answer the questions in your notes.

• Vestigial OrgansOrgans that are so reduced in size that they are “vestiges” or traces of homologous organs in other species. No longer have a known function.

Let’s Practice

•Complete the Cave Fish Activity in your notes.

Similarities in Embryology -Same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates.

See activity

Let’s Practice

•Answer the questions in your notes using the diagram on the next slide.

Molecular Biology

Differences in amino acid sequences and DNA sequences are greater between species that are more distantly related than between species that are more closely related.

Let’s Practice

•Comparing Amino Acid Sequence Lab

•Individual organisms in nature differ from one another

•Organisms produce more offspring than can survive, and many do not reproduce.

•Members of each species must compete for limited

resources.

•Each organism has different advantages and disadvantages for the struggle of existence.

• Individuals best suited to their environment survive and reproduce. Not suited will die off.

• Survival of the–fittest.

•Species change over time.

•Species alive today have descended

with modifications.

• All organisms on Earth are united into a single tree of life.

The study of genetic traits and changes in populations.

Gene pool

Is the combined genetic information of all the members of a particular population.

Allele frequencyIs the number of times that allele occurs in a

gene pool compared with the number of times other alleles occur.

Genetic equilibriumAllele frequencies remain constant.

Hardy-Weinberg principleAllele frequencies in a

population will remain constant unless one or more factors cause those frequencies to change.

5 Conditions to maintain equilibrium:

1. Random mating2. Population must be very

large3. No movement into/out of

population

4. No mutations

5. No natural selection

•Gene flowGene flow - movement of genes into/out of a population - introduces new alleles and/or changes allele frequencies:

Examples:–immigration, migration, transfer of breeding population

–movement of gametes: pollen, sperm & egg of ocean organisms

•Genetic DriftGenetic Drift - change that occurs due to chance - natural disasters (wipe out entire gene pools), mass migration (caribou, monarch butterfly), “bottlenecking” (cheetahs); has a greater effect on small populations.

•Non random matingNon random mating - monogamy, mate selection

•MutationsMutations –produce totally new alleles (sickle cell occurs randomly in 5/100,000,000.)

–May or may not affect an organism’s ability to adapt.

Let’s Practice

•Lab: Molecular Telephone

•Nature chooses which traits are best suited by selecting against certain characteristics; it is the most disruptive factor to genetic equilibrium!

1. Stabilizing Selection – average trait has the advantage

- Ex. Brown rabbits living in prairie grasses are better adapted than black or white rabbits. Therefore the black and white alleles are selected against and will be taken out of the gene pool.

Stabilizing SelectionAverage trait has the

advantage

2.Directional Selection – extremes have the advantage - ex. A fire burns the

prairie grasses. The Black rabbit is now better adapted. Therefore, the brown and white rabbits are selected against and are taken out of the gene pool.

Directional SelectionExtremes have the

advantage

3. Disruptive Selection – average trait has a disadvantage

- ex. Dark, tan and light colored limpets (shelled marine organisms) live on rocks. Sea gulls can’t see dark limpets on dark rocks or light limpets on light rocks. They can see the tan limpets on either rock color and will eat them.

Disruptive SelectionAverage trait has a

disadvantage

Let’s Practice

• Look at the graphs on your page and correctly label them.

•Any change in equilibrium causes changes in a population over a long period of time.

Let’s Practice

•Lab: Peppered Moth Survey

Before Industrial Revolution - 1845Before Industrial Revolution - 1845

After Industrial Revolution - 1890After Industrial Revolution - 1890

Speciation (formation of a new species)

• results from reproductive isolation- when members of two populations cannot interbreed and produce fertile offspring.

Behavioral IsolationTwo populations are capable of interbreeding but have differences in courtship rituals.

Eastern Meadowlark Western Meadowlark

Both birds are in thesame range howeverthey have a differentmating song.

http://www.mbr-pwrc.usgs.gov/id/framlst/Song/h5010so.mp3 http://www.naturesongs.com/weme1.wav

Geographic Isolation

Two populations separated by geographic barriers like rivers, and

mountains

Abert squirrel

Kaibab squirrel

Colorado River separatedthe species into two separatepopulations. Subspeciesformed -Kaibab squirrel

Temporal Isolation

Two or more species reproduce at

different times.Ex. Orchids in a rainforest

•Mass extinctions•Adaptive radiation•Convergent evolution•Coevolution•Punctuated equilibrium

More than 99% of all species that ever lived are now extinct

Wipes out whole ecological systems

ex. The dinosaurs

Fossils or living organisms show a single species or a small group of species have evolved into several forms that live in different ways.

Dinosaurs ruled 150 million years

Mammals remained small

When dino’s died out diversity of mammals occurred.

Unrelated organisms come to resemble one another.Shark is a fish, the penguin is a bird, and the dolphin is a mammal and all

swim.

Two species evolve in response to change in each other over time.

Ex. Orchid with a long spur contains a supply of nectar in its tip. An insect has an equally long feeding tube that enables it to feed on the nectar.

Describes a pattern of long, stable periods interrupted by brief periods of more rapid change.

•Changes in genes for growth and differentiation during embryological development could produce transformations in body shape and size. –Ex. ancient insects vs. modern insects

Present Day -smaller

Ancient Fossil -large