evolution everything you wanted to learn in the last week of school… you’re welcome! ~mrs....

Evolution

Everything you wanted to learn in the last week of school…

You’re welcome! ~Mrs. Boorom <3

Evolution Outline

Developing the theoryLamarckian evolution

Darwinian evolution

How evolution worksSelection pressure

Natural selection

Evidence of evolution

Antibiotic Resistance

Bacteria with a “good” variation are not affected by antibiotics.


Bacteria that aren’t killed by antibiotics pass on

there “antibiotic resistant” gene to their offspring,

resulting in a population with antibiotic resistant

genes.

Do species change over time?

YES!!!!!!!!!!!!!!!!!

Since the genes of the bacteria have changed (not antibiotic resistant to antibiotic resistant), the population eventually changed.

Do species change over time?

Evolution – change in the inherited characteristics in a species over time.

Differences Among Organisms

Variation – inherited trait that makes an individual different from other members of its species.

Genetic variation is caused by mutations.

Over time, more individuals inherit the mutation.

Ex. Differences in human hair lines

Differences Among Organisms

Adaptation – variation that makes an organism better suited for its environment

Helps an organism survive and reproduce.

May be physical, behavioral, or chemical.

Ex. camouflage

Theories Leading to Darwinian Evolution

Geologic ChangeHutton, 1795 & Lyell 1833

Layers of rock form very slowly, “nature” slowly shapes these rocks; Earth must be VERY OLD.

Must observe the present to understand the past.

Population GrowthThomas Malthus, 1798

Human population is increasing; as a result, resources will be limited.

Hypothesis of Acquired Characteristics

Jean Baptiste de Lamarck, early 1800’sTheory explaining how species change over time.

A parent may develop (acquire) certain traits that it “needs” to better survive in its environment. These acquired traits are passed on to its offspring. Evidence did not support this theory.


Giraffe needs a longer neck to reach the tree.Giraffe grows a longer neck because it needs to reach the tree. Longer neck trait is passed on to giraffe’s offspring. An organism can’t just “decide” to develop a particular trait because it would be beneficial.


An organism cannot develop a trait because it needs it to survive.

Traits must be inherited from parents or a genetic mutation must have occurred.

Artificial SelectionHumans selecting for favorable traits in offspring by choosing parents that have those traits.

Darwinian Evolution

Charles Darwin, 1850’s

Studied religion at the University

Traveled to the Galapagos Islands as a naturalist.

Read an economics book by Marx.

Studied inherited traits in pigeons, dogs, and flowers.

Developed a mechanism explaining how species change over time = natural selection

Darwinian evolution

Organisms do NOT inherit what they want.

Organisms can only inherit traits they have genes for.

Natural Selection

Explains HOW & WHY evolution occurs.

Organisms with inherited traits that are best suited to their environment are more likely to survive and reproduce, and pass on their “good” traits to future generations.

Darwinian Evolution

Selection pressure – something that influences the survival of an organism

Ex. Predators, chemicals, climate, food supply

Darwinian Evolution

Survival of the Fittest – individuals that are best suited for their environment will survive, reproduce, and pass their traits on to the next generation.

Genetics & Evolution

Some genetic differences help organisms survive & reproduce in their environment.

ALLELES GO TO OFFSPRING

Some genetic differences don’t help in survival & reproduction in that environment.

LESS ALLELES GO TO OFFSPRINGFrequency of unfavorable allele DECREASES

Factors Influencing Evolution

1) Genetics - inherited or from mutation

2) Environment - surroundings that influence survival and reproduction

How Populations Change

Gene Pool - All of the alleles for every gene present in a population.Relative Frequency

number of times an allele occurs in a gene pool compared the occurrence of other alleles.Environment determines which traits are “favorable.”

Evolution is the change of frequency of alleles in a population’s gene pool.

Effect of Natural Selection on a Population

Directional SelectionOne extreme form of a trait is most successful in the environment; the moderate and other extreme forms are less successful.


Stabalizing SelectionThe moderate form of a trait is most successful in the environment; BOTH extreme forms are less successful.


Disruptive SelectionBoth extreme forms of a trait are most successful in the environment; the moderate form is less successful.

Genetic Drift

Occurs in small populations.

Random chance may cause some alleles to occur more frequently in a population.

Speciation

As genetic differences accumulate in a population, a new species can develop.

Speciation – development of new species

Darwinian Evolution

Peppered Moth & Industrial Melanism

evolution everything you wanted to learn in the last week of school… you’re welcome! ~mrs....

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