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Ch. 4-3: Adapting To the Environment

Key Terms• Adaptation

• Coevolution

• Evolution

• Extinction

• Natural Selection

Ch.2 Section 3:Why Do I Need To Know This?

1. Because evolution has happened and

is continuing to happen.

2. Because every species has evolved

over time.

3. Because evolution helps to shape a

species and refine the niche for each species in an ecosystem.

Key Sections Ch. 2-3

• Adapting to the Environment

• Evolution By Natural Selection

• Genetics

• Mutations: Agents of Change

• Punctuated Equilibrium

• Coevolution

• Extinction

Adapting To the Environment

• Although it appears that most species are well suited to their environment, it is really a matter of those species that are well adapted to a specific environment surviving.

• No species can willingly adapt itself to its environment.

• Adaptation is the result of competition, mutation and natural selection.

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Evolution By Natural Selection

• Evolution is defined as the

change in a species over time.

• A species is a group of

organisms that can interbreed

with each other and produce fertile offspring with the same

basic characteristics.

• Three major scientists who

developed key scientific

understandings for genetics

are:

1. Charles Darwin

2. Gregor Mendel

3. Stephen Jay Gould

Evolution By Natural Selection

Evolution By Natural Selection

• Charles Darwin was a British biologist who lived from 1809 to 1882.

• In 1831 Darwin set sail around the world on a ship called the H.M.S. Beagle to study plants and animals.

• In 1832, the Beagle stopped in a group of very remote islands called the Galapagos Islands (off of South America).

• Darwin studied many of the birds there, particularly a small bird called the Finch.

Evolution By Natural Selection

• Finches are rather common small birds which cannot fly back and forth to South America.

• Darwin noticed that there were 13 different types of finches on all of the Galapagos Islands, but only 1 or 2 types on each individual island.

• And, Darwin noticed that the different types of finches had profoundly different beaks.

• He realized that the type of beak that occurred on each island related to the type of food that was available on the island.

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Evolution By Natural Selection

• Darwin realized that at one point a group of finches came to the Galapagos Islands. Some of the islands had trees with nuts, others did not.

• In that group of original finches, some finches had shorter beaks and some had longer beaks.

• Those that had shorter beaks were able to survive on the islands with trees with seeds, whereas those with longer beaks were able to survive on islands with insects.

• Over time, the finches that had the evolutionary advantages survived, whereas those with the disadvantage died out.

• Eventually, the populations on the island evolved to have only 1 or 2 species on each island, depending on the food availability and beak structure.

Evolution By Natural Selection

• Darwin published his Theory of Natural Selection in a book called On Origins of the Species.

• The Theory of Natural Selection states that:1. Within every species there is variation amongst

the members (some are taller/shorter/etc.).2. In every ecosystem, some traits will be favored

and some will not be favored.3. As a result, over time, those members with the

traits that are favored are more likely to survive and have offspring, leading to their favorable traits becoming more common within the species.

4. Eventually, if a trait becomes common to all members of a species, the species has evolved.

Artificial Selection• Selection under human direction

• Throughout history, humans have chosen and bred animals and plants with beneficial traits.

Genetics

• Gregor Mendel (1822-1884) was a Czeck monk/botanist who raised pea pods.

• He discovered that some pea pods had different colors and shapes.

• As Mendel bred the pea pods, he discovered that certain traits were passed onto the offspring and others were not.

• Mendel’s research led to the Punnett Square Diagram, making him the “father” of genetics!

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Genetics

• All of life is controlled by DNA.• An organism gets half of its DNA from its mother

and half of its DNA from its father.• While DNA is a very long molecule, portions of it

move together as genes.• There are 2 types of genes: Dominant genes

and Recessive genes.• Dominant genes are the genes that we will

actually see in an organism.• Recessive genes are not seen in an organism,

but can be passed onto the children.• In the Punnett Square, a dominant gene is

represented as a capital letter. A recessive geneis represented with a lower case letter.

Mechanisms of Biological Evolution: Genetic Drift and

Natural Selection

Genetic Drift

TEXTBOOK DEFINITION:

Natural Selection

Evolution that occurs by chance Process by which traits useful for survival and reproduction are passed on more frequently than those that are not

Genetics

The Punnett Square

Mutations: Agents of Change 1

• All cells reproduce inside a body to create new tissues.

• In order to create a new cell, a parent cell copies its DNA and creates a new set of DNA for the new cell which then splits off from the parent cell. This is called mitosis.

• During sexual reproduction, the egg and sperm cells undergo an extra step in which they split the DNA between the sex cells. This is called meiosis.

• This splitting is what gives a sex cell its dominant and recessive genes.

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Mutations: Agents of Change Mutations: Agents of Change 2

• Sometimes, during the copying stage of cell

division, the DNA is copied incorrectly.

• This incorrect copy of the DNA is called a mutation.

• If the mutation occurs during mitosis (normal

cell splitting) only that organism can be

affected by the mutation (it cannot pass that mutation onto its children).

• Some cancers are examples of mutations

that can occur during mitosis.

Mutations: Agents of Change 3

• If the mutation happens during meiosis (creation of sex cells) then the offspring WILL inherit the mutation and will be able to pass the mutation onto its offspring as well.

• Most mutations (about 99%) do not result in a live birth (the mother’s immune system detects it and destroys it or the mutation is too severe to survive).

• Those that do produce live offspring often do not have any benefit whatsoever and are called benign.

• However, over time, multiple mutations can occur within the species that could produce an evolutionary advantage.

• At some point, if enough mutations occur and get spread throughout the population, a new species will evolve!

Migration = Gene Flow

• Genes moving Into and out of an area is

also a source of genetic change

http://blog.nus.edu.sg

/lsm1303student2010/2010/04/06/where-they-were-born/

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Mechanisms of Biological Evolution:

Mutation and Migration

Mutation

Accidental change in DNA

that can give rise to

variation among individuals

Migration (gene flow)

Movement of individuals into

(immigration) or out of (emigration)

a population

Speciation

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are needed to see this picture.

• Process by which new species are generated

• Can occur in a number of different ways; the most important way is

called allopatric speciation

• Has resulted in every

form of life on Earth—today and in the past

Allopatric Speciation

Punctuated Equilibrium

• Stephen Jay Gould (1941 – 2004) was a geologist/biologist who taught at Harvard.

• He noticed that evolution typically happened when populations were isolated and undergoing environmental stress (such as a changing climate).

• Based on his research, he developed the Theory of Punctuated Equilibrium.

• According to punctuated equilibrium, a species achieves stability (no mutations) for long periods of time.

• However, when the environment changes, and populations of the species become isolated, the populations will either become extinct or will undergo massive amounts of mutation very quickly, most likely resulting in the rise of a new species.

Punctuated Equilibrium

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Coevolution

• Coevolution occurs when 2 or more species evolve in response to each other.

• Any relationship involving competition creates the potential for coevolution.

– Plants and herbivores coevolve in response to each other.

– Predators and prey coevolve in response to each other.

– Species in competition for limited resources often coevolve.

Extinction

• Extinction occurs when the last individual of a species dies.

• Although extinction occurs naturally, humans are presently causing extinction to occur at a rate that is about 1,000 times the natural rate.

Extinction• The disappearance of

species from Earth

• Generally occurs gradually, one species at a time, when environmental conditions change more

rapidly than the species can adapt

• There are five known mass extinction events, each of which wiped out a large proportion of Earth’s species.

Did You Know? During the Permo-Triassic extinction 250 million years ago, 70% of all

land species and 90% of all marine species

went extinct.

TrilobitesMarine arthropods that went extinct

at the end of the Permian period.