Which lion is more fit?

Warm Up

Describe what is happening in the picture above.

How is the population of mice different in figure 3 than in figure 1?

Engage• What are the advantages of these animals’

camouflage?• What are their chances of survival in different

environments? Explain.

What is Evolution?

• Evolution means to change over time.

• This is the process by which modern organisms have descended from ancient organisms.

Darwin’s Theory of Evolution by Natural Selection• Charles Darwin was a

naturalist who observed many species.

• He is famous for his trips to the Galapagos Islands, his observations of the finches (and other animals) and the book he wrote: “On The Origin of Species”

Darwin’s Theory of Evolution by Natural Selection• He collected and studied fossils (preserved

remains of ancient organisms) and compared them to living animals

• By looking at the diagram above, on which island does vegetation grow close to the ground?

• On which island does it grow higher on trees?

Fitness • The ability of an organism to

survive and reproduce

• An organism with an adaptation is more fit to survive in its environment, and will reproduce. Its DNA (with the codes for the adaptation) gets passed on to its offspring.

• Fit offspring then survive and reproduce and even more offspring are “born” that have the adaptation.

• Over generations, the DNA in the whole population changes, so that all the population has the adaptation that makes the population fit for its environment.

“Survival of the Fittest”

• Faster, stronger, good hunter, better camouflaged

Natural Selection=Survival of the Fittest

1. Variation exists among individuals in a species.2. Individuals of species compete for resources (food and space).

3. Some competition leads to the death of some individuals while others survive.4. Individuals that have beneficial variations are more likely to survive and reproduce.

Variation

Variation exists within the gene pool of every population. This variation is the result of random gene mutations and translation errors.

Nature basically “selects” certain individuals to be successful and reproduce and over time the population changes due to this selection.

Types of Selection

Disruptive Selection

• Describes changes in population genetics in which extreme values for a trait are favored over medium values.

• The variance of the trait increases and the population is divided into 2 distinct groups.

Copyright Pearson Prentice Hall

Disruptive Selection 

When individuals at the upper and lower ends of the curve have higher fitness than individuals near the middle, disruptive selection takes place.

Stabilizing Selection• Describes changes in population genetics

in which extreme phenotypes for a trait are not favored over medium values.

• Extreme phenotypes give individuals a disadvantage.

Copyright Pearson Prentice Hall

Stabilizing Selection 

When individuals near the center of the curve have higher fitness than individuals at either end of the curve, stabilizing selection takes place.

Copyright Pearson Prentice Hall

Directional Selection 

When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end, directional selection takes place.

Results of Natural Selection

1. Adaptation-any inherited characteristic that increases an organisms chances of survival.

2. Speciation- formation of a new species

3. Extinction- disappearance of a species from all parts of its geographical range.

• Adaptation – any inherited characteristic that increases an organism’s chance of survival. (Remember the source of any new trait is a mutation.)

• Adaptations make an organism better suited to the environment. So in the struggle for survival, organisms with adaptations suited to the environment will be more likely to survive and reproduce.

AdaptationsThe favorable variations are called Adaptations. They are key for survival.

These peppered moths are a good example of industrial melanism.

Peppered moth: Evolution in action

Year % dark % light1848 5 951895 98 21995 19 81

clean air, light-colored bark

pollution, dark-colored bark

Clean Air Act, light-colored bark

industrial melanism

Adaptations • This frogfish is

perfectly adapted to its environment.

• The porcupine has adapted sharp quills that make it difficult for other animals to eat it.

Speciation-creates a new species.

Speciation will occur when the gene pools of two populations become separated.

Behavioral Isolation: Two or more populations are capable of interbreeding, but won’t because of courtship rituals.

Temporal Isolation: Two or more species reproduce at different times.

_____________ Isolation

• Ex. meadowlarks using 2 different songs to attract mates

________________ Isolation

• Ex. orchids that pollinates once a year

Speciation

Geographic Isolation: Two or more populations are separated by geographical barriers such as mountains or rivers.

Extinction

Simply put, those who are not well adapted to their environment do not survive and reproduce. This means they eventually become extinct.

The dinosaurs could not adapt well to the sudden change in their environment, so they became extinct.

Extinction!How bad would it be to lose the polar bear forever?

• Global warming has caused glaciers to melt.

• Polar bears must swim further distances between each iceflow.

• As the distances increase, more polar bears are drowning.

Survival of the Fittest!?

As the polar bears lose their habitat, some are crossing into grizzly bear territory. As they try to adapt to the grizzly bear habitat, they are also beginning to breed with them.

Natural Selection Summary Points for Reproductive Success

1. Inherited variation – there are genetic variations (differences) between individuals of a population

• The more genetic diversity, the more variations of alleles that are suited for the environment. The more offspring will survive and reproduce.

• The population will then continue.

Natural Selection Summary Pointsfor Reproductive Success

2. Overproduction of offspring – there are more offspring are produced than can survive

3. Struggle for existence – there is competition for survival among the members of the population

Genetic Variation(Inherited)

• variation in alleles of genes that occurs both within and among populations

Peppered moth(Example of Genetic Variation)

• Why did the population change?– early 1800s = pre-industrial England

• low pollution• lichen on trees = light colored bark

– late 1800s = industrial• factories = soot coated trees• killed lichen = dark colored bark

– mid 1900s = pollution controls• clean air laws• return of lichen = light colored

bark

• Peppered Moth– 2 types: dark vs. light

Peppered moth