THE DIVERSITY OFTHE DIVERSITY OFLIFELIFE

SPECIES SCAPESPECIES SCAPE

NUMBERS OF CURRENT NUMBERS OF CURRENT SPECIESSPECIES

BIODIVERSITYBIODIVERSITY Biodiversity refers to the variety of Biodiversity refers to the variety of

organisms and their genetic diversity on organisms and their genetic diversity on our planet our planet

Today over 1.5 million living and 300,000 Today over 1.5 million living and 300,000 extinct species have been named and extinct species have been named and described described

With this tremendous amount of diversity With this tremendous amount of diversity the question becomes “Why or how are the question becomes “Why or how are there so many forms of life on our planet?” there so many forms of life on our planet?”

The answer to this question is evolution The answer to this question is evolution Today biologists use the process of Today biologists use the process of

evolution to explain the diversity and evolution to explain the diversity and relationships of life on our planet relationships of life on our planet

MAIN POINTS OF MAIN POINTS OF REVIEWREVIEW Biological evolution explains the diversity Biological evolution explains the diversity

of lifeof life The fossil record gives evidence for The fossil record gives evidence for

natural selection and its evolutionary natural selection and its evolutionary consequencesconsequences

Organisms can be classified based on Organisms can be classified based on evolutionary relationshipsevolutionary relationships

The similarity of DNA (genetic) The similarity of DNA (genetic) sequences gives evidence of relationships sequences gives evidence of relationships between organismsbetween organisms

The extinction of species can be a natural The extinction of species can be a natural processprocess

Biological evolution Biological evolution explains the diversity of lifeexplains the diversity of life

Evolution or descent with modification Evolution or descent with modification explains how the gene pools of species or explains how the gene pools of species or populations change over time leading to populations change over time leading to the development of new species and the development of new species and therefore diversity of life therefore diversity of life

These are members of different species - These are members of different species – eastern (left) and western (right) meadowlark.

Biologists have described Biologists have described several mechanisms that several mechanisms that

lead to changeslead to changes They include:They include: MutationsMutations Gene recombinationGene recombination Gene flowGene flow Genetic driftGenetic drift Natural SelectionNatural Selection

DARWIN & NATURAL DARWIN & NATURAL SELECTIONSELECTION

Nature produces variations Nature produces variations within members of the within members of the same species or population same species or population which can result in uneven which can result in uneven advantages in their ability advantages in their ability to survive to survive

Over time this can result in Over time this can result in the change in the gene the change in the gene pool of a species pool of a species

This process can lead to This process can lead to enough change that over enough change that over time a new species appears time a new species appears

New species means New species means increased biodiversity increased biodiversity

THE ORIGIN OF THE ORIGIN OF SPECIESSPECIES

Darwin’s theory was based on Darwin’s theory was based on four premises: four premises:

1. Variations exist among 1. Variations exist among individuals within the same individuals within the same species. species.

2. All organisms produce more 2. All organisms produce more offspring that are able to offspring that are able to survive. survive.

3. Competition for space, food, 3. Competition for space, food, other survival needs leads to the other survival needs leads to the elimination of some organisms elimination of some organisms of each population.of each population.

4. The organisms that have 4. The organisms that have variations which enable them to variations which enable them to survive within their environment survive within their environment and through competition, are and through competition, are the ones most likely to survive the ones most likely to survive and reproduce, thereby passing and reproduce, thereby passing their characteristics on to their their characteristics on to their offspring (survival of the fittest, offspring (survival of the fittest, or natural selection) or natural selection)

REVIEWREVIEW1. Natural selection can best be defined as the1. Natural selection can best be defined as the

a. survival of the biggest and strongest organisms in a populationa. survival of the biggest and strongest organisms in a populationb. elimination of the smallest organisms by the biggest organismsb. elimination of the smallest organisms by the biggest organismsc. survival and reproduction of the organisms that occupy the largest areac. survival and reproduction of the organisms that occupy the largest aread. survival and reproduction of the organisms that are genetically best d. survival and reproduction of the organisms that are genetically best adaptedadapted

2. The major unifying concept in biology that provides for an explanation for the 2. The major unifying concept in biology that provides for an explanation for the vast diversity of life on our planet isvast diversity of life on our planet isa. the theory of evolution.a. the theory of evolution.b. the cell theory.b. the cell theory.c. the classification theorem.c. the classification theorem.d. gene-chromosome theorem.d. gene-chromosome theorem.

3. In the illustration to the right, which answer best explains the difference3. In the illustration to the right, which answer best explains the difference in the length of the animals’ necks?in the length of the animals’ necks?

a. The theory of use and disuse.a. The theory of use and disuse.b. The change in gene pool due to mutation.b. The change in gene pool due to mutation.c. The theory of natural selection.c. The theory of natural selection.d. The desire for organisms to change and adapt.d. The desire for organisms to change and adapt.

4. Genetic variations are the raw material for evolution. These variations cannot 4. Genetic variations are the raw material for evolution. These variations cannot be acted upon by natural selection unlessbe acted upon by natural selection unlessa. they are expressed in the phenotype of the organism.a. they are expressed in the phenotype of the organism.b. they produce only unfavorable characteristics.b. they produce only unfavorable characteristics.c. they produce only favorable characteristics.c. they produce only favorable characteristics.d. they are expressed in non-sex cells.d. they are expressed in non-sex cells.

THE FOSSIL RECORD THE FOSSIL RECORD GIVES EVIDENCE FOR GIVES EVIDENCE FOR

EVOLUTIONEVOLUTION The study of fossils is called paleontology The study of fossils is called paleontology The study of rocks and land formations is The study of rocks and land formations is

called geology called geology Fossils are the remains of once living Fossils are the remains of once living

organisms organisms The most common types of fossils form The most common types of fossils form

when shells, bones, or other parts of when shells, bones, or other parts of organisms are rapidly covered with organisms are rapidly covered with layers of sediment layers of sediment

Fossils are found in sedimentary rocks Fossils are found in sedimentary rocks Sedimentary rock forms in layers Sedimentary rock forms in layers

GEOLOGIC TIME SCALEGEOLOGIC TIME SCALE

Different types of fossils are found in different Different types of fossils are found in different aged layers of rock aged layers of rock

Therefore, the fossil record supports evolutionary Therefore, the fossil record supports evolutionary theory by providing evidence that organisms that theory by providing evidence that organisms that have lived in the past did change over timehave lived in the past did change over time

This is evidence that the kinds of plants and This is evidence that the kinds of plants and animals, and other organisms have changed over animals, and other organisms have changed over time and is called the Law of Fossil Succession time and is called the Law of Fossil Succession

REVIEW QUESTIONSREVIEW QUESTIONS 1. Why is a mammoth more likely to fossilize than a 1. Why is a mammoth more likely to fossilize than a

caterpillar?caterpillar? a. hard parts such as bones and teeth fossilize easier a. hard parts such as bones and teeth fossilize easier

than soft parts. than soft parts. b. mammoths lived a long time ago and caterpillars b. mammoths lived a long time ago and caterpillars

live today.live today. c. large organisms tend to fossilize easier than small c. large organisms tend to fossilize easier than small

organisms. organisms. d. caterpillars have too short of a life span for d. caterpillars have too short of a life span for

fossilization to occur. fossilization to occur.

2. Some organisms never become fossils because2. Some organisms never become fossils because a. they live in water environments where no fossils a. they live in water environments where no fossils

form.form. b. they are destroyed after death so nothing remains b. they are destroyed after death so nothing remains

to be fossilized.to be fossilized. c. a hard shells prevent fossilization from occurring.c. a hard shells prevent fossilization from occurring. d. there are no minerals in the soil where the organism d. there are no minerals in the soil where the organism

dies. dies.

4. Which of the following is one reason that fossils from 4. Which of the following is one reason that fossils from all organisms where ever alive will all organisms where ever alive will NEVERNEVER be found? be found?

a. organisms moved from one place to another, so the a. organisms moved from one place to another, so the location of some fossils will never be found.location of some fossils will never be found.

b. some parts of the world have never had sedimentary b. some parts of the world have never had sedimentary rock, and therefore fossils could not formrock, and therefore fossils could not form

c. some animals consume fossils and therefore, there are c. some animals consume fossils and therefore, there are none left to be found. none left to be found.

d. many organisms that have lived had no hard solid d. many organisms that have lived had no hard solid structures that survived long enough to be fossilized. structures that survived long enough to be fossilized.

5. Several fossils were uncovered in different layers of 5. Several fossils were uncovered in different layers of rock in a desert area. The following diagram indicates rock in a desert area. The following diagram indicates the fossils found and the layers they were found in. the fossils found and the layers they were found in.

Based on the fossils found, this area was most likely once Based on the fossils found, this area was most likely once a a

a. forest that was replaced by a lakea. forest that was replaced by a lake b. lake that was replaced by a forestb. lake that was replaced by a forest c. an ocean that was replaced by a forestc. an ocean that was replaced by a forest d. a lake that was replaced by a desert. d. a lake that was replaced by a desert.

Similarity of DNA sequences Similarity of DNA sequences gives evidence of relationshipsgives evidence of relationships

The building blocks, called nucleotides, that make up The building blocks, called nucleotides, that make up the DNA in all organisms are the same: A, T, G, and C the DNA in all organisms are the same: A, T, G, and C

It is the sequence of these nucleotides, and ultimately It is the sequence of these nucleotides, and ultimately the the numbernumber, , typetype, and , and sequencesequence of genes that makes of genes that makes one organism different from another one organism different from another

DNA of many organisms and the similarity between DNA of many organisms and the similarity between DNA samples is used to determine relationships DNA samples is used to determine relationships between organisms between organisms

Organisms can be classified Organisms can be classified based on evolutionary based on evolutionary

relationshipsrelationships

Because biological evolution involves genetic changes Because biological evolution involves genetic changes (mutations) over time, the evolutionary relationship of (mutations) over time, the evolutionary relationship of organisms can be determined by comparing DNA organisms can be determined by comparing DNA

Different species with very similar DNA more recently Different species with very similar DNA more recently descended from a common ancestor than did species with descended from a common ancestor than did species with very different DNA very different DNA

Because DNA codes for the production of proteins, Because DNA codes for the production of proteins, comparison of proteins between species also provides comparison of proteins between species also provides evolutionary relationships between organisms evolutionary relationships between organisms

CLASSIFICATION OF CLASSIFICATION OF LIFELIFE

Organisms can be classified into groups Organisms can be classified into groups based on morphological, behavioral, based on morphological, behavioral, and evolutionary relationships and evolutionary relationships

Classifying organisms is important to Classifying organisms is important to scientists as it provides a framework scientists as it provides a framework and a common “language” which and a common “language” which enables scientists everywhere to study enables scientists everywhere to study and understand more about life on and understand more about life on Earth Earth

Taxonomy is the science of Taxonomy is the science of classification classification

Scientists currently Scientists currently recognize 3 Domains recognize 3 Domains

The Linnean system of The Linnean system of classificationclassification

Domain, Kingdom, Phylum, Domain, Kingdom, Phylum, Class, Order, Family, Class, Order, Family,

Genus, SpeciesGenus, Species CategoryCategory Domestic cat Domestic cat Domain Domain EucaryaEucarya KingdomKingdom Animalia (animals) Animalia (animals) Phylum/DivisionPhylum/Division Chordata (chordates) Chordata (chordates) ClassClass Mammalia (mammals) Mammalia (mammals) OrderOrder Carnivoria (carnivores) Carnivoria (carnivores) FamilyFamily Felidae (cats) Felidae (cats) GenusGenus FelisFelis SpeciesSpecies silvestrissilvestris

REVIEW QUESTIONSREVIEW QUESTIONS 1. A horse and a donkey may 1. A horse and a donkey may

interbreed with each other and interbreed with each other and produce offspring. The offspring are produce offspring. The offspring are generally sterile, however, because generally sterile, however, because the horse and the donkey are of the horse and the donkey are of differentdifferent

a. ordersa. orders b. kingdomsb. kingdoms c. speciesc. species d. phylad. phyla

2. The following illustration 2. The following illustration represents a phylogenetic tree which represents a phylogenetic tree which includes several different organisms. includes several different organisms. Based upon this diagram, which of the Based upon this diagram, which of the following groups of organisms have following groups of organisms have the closest evolutionary relationship? the closest evolutionary relationship?

a. mammals and lizardsa. mammals and lizards b. mammals and frogsb. mammals and frogs c. lungfish and frogsc. lungfish and frogs d. lizards and snakesd. lizards and snakes

3. Which of the following would provide the best 3. Which of the following would provide the best data for determining the phylogeny (evolutionary data for determining the phylogeny (evolutionary history) of three very closely related species?history) of three very closely related species?

a. fossil recordsa. fossil records b. comparison of anatomical structuresb. comparison of anatomical structures c. comparisons of their scientific namesc. comparisons of their scientific names d. comparison of DNA sequencesd. comparison of DNA sequences

4. Which of the following characteristics did 4. Which of the following characteristics did Linnaeus use to classify organisms?Linnaeus use to classify organisms?

a. DNA similaritiesa. DNA similarities b. Environments in which the organisms livedb. Environments in which the organisms lived c. The color of the fur, skin, or feathersc. The color of the fur, skin, or feathers d. Shape, size and structured. Shape, size and structure

The extinction of species The extinction of species can be a natural processcan be a natural process

Extinctions occur “often” in Extinctions occur “often” in evolutionary history evolutionary history

Scientists estimate that more than Scientists estimate that more than 90% of the species that have lived on 90% of the species that have lived on earth are probably extinct earth are probably extinct

Most extinctions occur due to Most extinctions occur due to selective nature of the species selective nature of the species

The fossil record provides evidence The fossil record provides evidence that background extinctions that background extinctions regularly occur throughout time regularly occur throughout time

MASS EXTINCTIONSMASS EXTINCTIONS Scientific studies show another type of Scientific studies show another type of

extinction in which massive numbers of extinction in which massive numbers of species become extinct in a short period species become extinct in a short period of time of time

These are called mass extinctions These are called mass extinctions There are 5 recognizable periods of There are 5 recognizable periods of

mass extinction in the earth’s history mass extinction in the earth’s history There are several theories as to the There are several theories as to the

cause of the mass extinctions, most of cause of the mass extinctions, most of which hypothesize that major climatic which hypothesize that major climatic and environmental changes occurred and environmental changes occurred globally globally

A graph of invertebrate extinctions over the last 600 million years. The mass extinctions appear as periodic peaks rising above the background

extinction levels. This data is from the work of D. M. Raup and J. J. Sepkoski.

MORE ON EXTINCTIONMORE ON EXTINCTION The extinction of a species can occur The extinction of a species can occur

through the process of evolution through the process of evolution Extinction by natural causes may be due Extinction by natural causes may be due

either to actual death of a species or due either to actual death of a species or due to evolution of the species into one or to evolution of the species into one or more different species more different species

Evidence from the fossil records Evidence from the fossil records substantiates that many species have substantiates that many species have become extinct and new species have become extinct and new species have developed over time developed over time

Many scientists believe that Earth may be Many scientists believe that Earth may be in a 6th mass extinction phase, as many in a 6th mass extinction phase, as many species are going extinct every day species are going extinct every day

REVIEW QUESTIONSREVIEW QUESTIONS 1. Which of the following has 1. Which of the following has NOTNOT been implicated as been implicated as

contributing to mass extinctions?contributing to mass extinctions? a. volcano eruptionsa. volcano eruptions b. changes in ocean water levelb. changes in ocean water level c. major hurricanesc. major hurricanes d. asteroid impactd. asteroid impact

2. What percent of species that have ever lived on earth are 2. What percent of species that have ever lived on earth are probably extinct?probably extinct?

a. 28%a. 28% b. 52%b. 52% c. 77%c. 77% d. 90%d. 90%

3. Which of the following does 3. Which of the following does NOTNOT likely contribute to likely contribute to background extinctions?background extinctions?

a. evolution through natural selectiona. evolution through natural selection b. destruction of a habitat due to natural or human causeb. destruction of a habitat due to natural or human cause c. interbreeding between speciesc. interbreeding between species d. changes in local environmental conditionsd. changes in local environmental conditions

4. The following diagram illustrates numbers of 4. The following diagram illustrates numbers of extinctions that have occurred over time. What is the extinctions that have occurred over time. What is the highest rate of background extinction indicated in this highest rate of background extinction indicated in this diagram?diagram?

a. 10 families per million yearsa. 10 families per million years b. 7 families per million years b. 7 families per million years c. 17 families per million years c. 17 families per million years d. 5 families per million years d. 5 families per million years