Changes

in Species

Over Time

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Age of EarthAge of Earth

Scientist believe that the Earth is 4.6

Billion years old.

•Evidence:

Rock data, environmental changes

22CLIP

Natural Selection•Also know as “survival of the fittest.•Only certain members of the population will survive and reproduce.•Ones that are most suited to the environment.

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If an organism reproduces, then

the traits of that organism are

passed to the next generation.

Traits that are favorable for a

certain environment become

more prevalent within that

population.

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What if the environment What if the environment changes?changes?

The organisms must adapt to the environment. Those that

don’t adapt-die.This is a very slow process….does

not occur over night…many generations must past before

any change in the population can be seen.

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Example: Peppered MothExample: Peppered Moth

Two

versions of

the moth-

Black

and

peppere

dDuring

the

industrial

revolution

on England

Populatio

n of moths

changed66

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Decent with modificationsOvertime

natural selection

produces

organisms

that have

different

structures,

established

different

niches, or occupy

different

habitats.

Organisms that were once the same have now grown “apart” and have become different organisms.88

These changes increase a species’

fitness in their environment.

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History• James Hutton -1785-Propsed

that he Earth is millions of years old.

• Thomas Malthus -1798-proposed that populations outgrew their food supplies, causing competition between organisms and a struggle for one species to survive against another

• Jean-Baptiste Lamark -1809-believed that all life forms evolved and that the driving force of evolution was the inheritance of acquired characteristics. He believed that organisms changed due to the demands of their environment. 1111

•Lylle -1833-proposed that plant and animal species had arisen, developed variations, and then became extinct over time. He also believed that the Earth’s physical landscape changed over a long period of time. •Alfred Russel Wallace -1858-emphasis was based on the idea of competition for resources as the main force in natural selection •Charles Darwin -1859- Publishes “On the Origin of Species”

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Charles Darwin

British Naturalist

1809 -1882

“I have called this principle, by

which each slight variation, if

useful, is preserved, by the

term Natural Selection.”

—Charles Darwin from "The Origin

of Species"

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From 1831 to 1836

Darwin served as

naturalist aboard

the H.M.S. Beagle on

a British science

expedition around

the world. In South

America Darwin

found fossils of

extinct animals that

were similar to

modern species. On

the Galapagos

Islands in the Pacific

Ocean he noticed

many variations

among plants and

animals of the same

general type as

those in South

America. 1144

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Humans select and breed for certain traits.

Examples: The largest hog, the cow that gives the most milk, or fastest horse.

Artificial selection provides a model that helps us understand natural selection.People have been artificially selecting domesticated plants and animals for thousands of years. These activities have amounted to large, long-term, practical experiments that clearly demonstrate that species can change dramatically through selective breeding. Broccoli and brussels sprouts bear little superficial resemblance to their wild mustard relatives (left).

Evidence for Change Over TimeFossil Record

–Fossils that show how the same organism looked millions of years ago.

–Paleontology –Use rock layers– Isotope dating

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1177

Relative Dating

1188

Homologous

structures

Structures

that have

different

mature

forms in

different

organisms

but have

developed

from the

same type

of tissue.1199

Homologous structures

2200

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•Embryology–Early development of the organism

Stages of developmen

tp385

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Vestigial organsVestigial organs–Organs or structures Organs or structures that do not seem to be that do not seem to be used by the organism used by the organism any longer. any longer.

–They are usually They are usually reduced in size.reduced in size.

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Vestigial Organs

c

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2255

GeneticsGenetics

DNA sequences in

organisms are close

Sources of genetic

variation in species:

1.Mutations

2.Gene Shuffling

3.Crossing over

during meiosis

•Speciation •is the evolution of a new species that occurs when interbreeding happens, or when the production of fertile offspring is prevented. In the physical world, natural barriers form and cause the breakup of populations to form smaller populations.Volcanoes, sea-level changes, and earthquakes are a few examples of natural occurrences that affect populations

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•Overtime they can change so much that they become unable to breed as they adapt to their environment.

Speciation Mechanisms• Behavioral Isolation

– Populations are capable of interbreeding, but have different courtship rituals or other type of behavior.

• Geographic Isolation– Separated by bodies of water or mountains.

• Temporal Isolation– Reproduction takes place at different times of the year

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Gene Pool•Combined

genetic

information

of a particular

population.

•All the

genes present with

in a population

•Can change

Changes in allele frequency with in a population

Genetic drift

•Random changes in allele frequency

that occurs in small populations

•Also know as the “founder effect”

•Populations may move into a new area

and the alleles that carry with them will

be passed on to their offspring.

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Divergent Evolution

•Divergent evolution is the process of two or more related species becoming more and more dissimilar.•The red fox and the kit fox provide and example of two species that have undergone divergent evolution. •As they adapted to different environments, the appearance of the two species diverged.

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Convergent Convergent EvolutionEvolution

•Convergent evolution is the emergence of biological structures

or species that exhibit similar function and appearance but that

evolved through widely different evolutionary pathways.•examples include

the multiple origins

of wings (bats, birds) and eyes.

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Coevolution•Predators and their prey •Parasites and their hosts•Plant-eating animals and the plants upon which they feed •One example of coevolution is between plants and the animals that pollinate them.

Coevoluti

on is the

joint

change of

two or

more

species in

close

interactio

n.

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Evolution at the species level is called microevolution.

It results from genetic variation and natural selection within a population of organisms.

Macroevolution is evolution that occurs between different species.

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Evolution is the change in

a species over time.

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Rates of Evolution3399

Gradualism Gradualism && Punctuated Equilibrium Punctuated Equilibrium• Two ways in

which the evolution of a species can occur.

• A species can evolve by only one of these, or by both.

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•Species with a shorter evolution evolved mostly by punctuated equilibrium, and those with a longer evolution evolved mostly by gradualism.

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GradualismGradualism•Very gradually, over a long time... Over a short period of time it is hard to notice. •Small variations that fit an organism slightly better to its environment are selected for: a few more individuals with more of the helpful trait survive, and a few more with less of the helpful trait die.•Change is slow, constant, and consistent.

Punctuated equilibriumPunctuated equilibrium•change comes in spurts. There is a period of very little change, and then one or a few huge changes occur, often through mutations in the genes of a few individuals.

Resistance in Bacteria

4242 Read page p403.

Two main sources of Two main sources of genetic variationgenetic variation

1.1.MutationsMutations

2.2.Genetic ShufflingGenetic Shuffling

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EOCT- It is important that you are able to explain how the concepts of genetics provide the basis for explaining natural selection and evolution. This will help you answer questions

like this:

What is the end result of natural selection?

A increased number of offspring of a given phenotype that survive

B changes in the frequency of alleles in a population

C fossil formation through extinctionD environmental changes of a habitat

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Although the Arctic fox and the kit fox are closely related, they look very different because the individualsA acquired traits during their lifetimes that contributed to survivalB with traits most suited to their environments reproduced most successfullyC migrated long distances to environments that most suited their traitsD passed on to their offspring acquired behaviors that were helpful

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Fossils of Archeopteryx show that this animal had feathers, like a bird. It also had a bony tail, teeth, and claws on its wings, like a reptile. This fossil is evidence that supports the idea thatA birds and reptiles have a common ancestorB birds have changed very little over 150 million yearsC reptile species are more advanced than bird speciesD reptiles are warm-blooded like birds

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Horses and tapirs have a common ancestor, but Horses and tapirs have a common ancestor, but now look very different. Horses now are grassland now look very different. Horses now are grassland animals adapted for grazing on grass and shrubs. animals adapted for grazing on grass and shrubs. Tapirs are jungle animals that live in dense forests Tapirs are jungle animals that live in dense forests and eat fruit, leaves and aquatic vegetation. Which and eat fruit, leaves and aquatic vegetation. Which of the following led to the development of such of the following led to the development of such differences in the two species?differences in the two species?

A selective breedingA selective breedingB convergent evolutionB convergent evolutionC DNA hybridizationC DNA hybridizationD natural selectionD natural selection

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Review CLIP

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Adaptation is the key concept in natural selection.

• Adaptation is a key concept in natural selection.

• Natural selection can change the inherited characteristics in a population and possibly even result in a new species.

The environment affects the evolution of living things.

House sparrows arrived in North America from Europe in the nineteenth century. Since then, genetic variation within the population, and selection in various habitats, have allowed them to inhabit most of the continent. House sparrows in the north are larger and darker colored than those in the south. Darker colors absorb sunlight better than light colors and larger size allows less surface area per unit volume, thus reducing heat loss—both advantages in a cold climate. This is an example of natural selection acting upon a population, producing micro-evolution on a continental scale.

• Proposed by Charles Darwin, natural selection is the process by which organisms that are best suited to their environment survive and pass their genetic traits on to their offspring.