THE DIVERSITY OF LIFE

1. THE DIVERSITY OFLIFE

2. SPECIES SCAPE

3. NUMBERS OF CURRENT SPECIES

4. BIODIVERSITY • Biodiversity refers to the variety of organisms and their genetic diversity on our planet • Today over 1.5 million living and 300,000 extinct species have been named and described • With this tremendous amount of diversity the question becomes “Why or how are there so many forms of life on our planet?” • The answer to this question is evolution • Today biologists use the process of evolution to explain the diversity and relationships of life on our planet

5. MAIN POINTS OF REVIEW • Biological evolution explains the diversity of life • The fossil record gives evidence for natural selection and its evolutionary consequences • Organisms can be classified based on evolutionary relationships • The similarity of DNA (genetic) sequences gives evidence of relationships between organisms • The extinction of species can be a natural process

6. Theseare members of different species - These are members of different species – eastern (left) and western (right) meadowlark. Biological evolution explains the diversity of life • Evolution or descent with modification explains how the gene pools of species or populations change over time leading to the development of new species and therefore diversity of life

7. Biologists have described several mechanisms that lead to changes They include: • Mutations • Gene recombination • Gene flow • Genetic drift • Natural Selection

8. DARWIN & NATURAL SELECTION • Nature produces variations within members of the same species or population which can result in uneven advantages in their ability to survive • Over time this can result in the change in the gene pool of a species • This process can lead to enough change that over time a new species appears • New species means increased biodiversity

9. THE ORIGIN OF SPECIES • Darwin’s theory was based on four premises: • 1. Variations exist among individuals within the same species. • 2. All organisms produce more offspring that are able to survive. • 3. Competition for space, food, other survival needs leads to the elimination of some organisms of each population. • 4. The organisms that have variations which enable them to survive within their environment and through competition, are the ones most likely to survive and reproduce, thereby passing their characteristics on to their offspring (survival of the fittest, or natural selection)

10. REVIEW 1. Natural selection can best be defined as the a. survival of the biggest and strongest organisms in a population b. elimination of the smallest organisms by the biggest organisms c. survival and reproduction of the organisms that occupy the largest area d. survival and reproduction of the organisms that are genetically best adapted 2. The major unifying concept in biology that provides for an explanation for the vast diversity of life on our planet is a. the theory of evolution. b. the cell theory. c. the classification theorem. d. gene-chromosome theorem. 3. In the illustration to the right, which answer best explains the difference in the length of the animals’ necks? a. The theory of use and disuse. b. The change in gene pool due to mutation. c. The theory of natural selection. d. The desire for organisms to change and adapt. 4. Genetic variations are the raw material for evolution. These variations cannot be acted upon by natural selection unless a. they are expressed in the phenotype of the organism. b. they produce only unfavorable characteristics. c. they produce only favorable characteristics. d. they are expressed in non-sex cells.

11. THE FOSSIL RECORD GIVES EVIDENCE FOR EVOLUTION • The study of fossils is called paleontology • The study of rocks and land formations is called geology • Fossils are the remains of once living organisms • The most common types of fossils form when shells, bones, or other parts of organisms are rapidly covered with layers of sediment • Fossils are found in sedimentary rocks • Sedimentary rock forms in layers

12. GEOLOGIC TIME SCALE • Different types of fossils are found in different aged layers of rock • Therefore, the fossil record supports evolutionary theory by providing evidence that organisms that have lived in the past did change over time • This is evidence that the kinds of plants and animals, and other organisms have changed over time and is called the Law of Fossil Succession

13. REVIEW QUESTIONS • 1. Why is a mammoth more likely to fossilize than a caterpillar? • a. hard parts such as bones and teeth fossilize easier than soft parts. • b. mammoths lived a long time ago and caterpillars live today. • c. large organisms tend to fossilize easier than small organisms. • d. caterpillars have too short of a life span for fossilization to occur. • 2. Some organisms never become fossils because • a. they live in water environments where no fossils form. • b. they are destroyed after death so nothing remains to be fossilized. • c. a hard shells prevent fossilization from occurring. • d. there are no minerals in the soil where the organism dies.

14. 4. Which of the following is one reason that fossils from all organisms where ever alive will NEVER be found? a. organisms moved from one place to another, so the location of some fossils will never be found. b. some parts of the world have never had sedimentary rock, and therefore fossils could not form c. some animals consume fossils and therefore, there are none left to be found. d. many organisms that have lived had no hard solid structures that survived long enough to be fossilized. 5. Several fossils were uncovered in different layers of rock in a desert area. The following diagram indicates the fossils found and the layers they were found in. Based on the fossils found, this area was most likely once a a. forest that was replaced by a lake b. lake that was replaced by a forest c. an ocean that was replaced by a forest d. a lake that was replaced by a desert.

15. Similarity of DNA sequences gives evidence of relationships • The building blocks, called nucleotides, that make up the DNA in all organisms are the same: A, T, G, and C • It is the sequence of these nucleotides, and ultimately the number, type, and sequence of genes that makes one organism different from another • DNA of many organisms and the similarity between DNA samples is used to determine relationships between organisms

16. Organisms can be classified based on evolutionary relationships

17. Because biological evolution involves genetic changes (mutations) over time, the evolutionary relationship of organisms can be determined by comparing DNA • Different species with very similar DNA more recently descended from a common ancestor than did species with very different DNA • Because DNA codes for the production of proteins, comparison of proteins between species also provides evolutionary relationships between organisms

18. CLASSIFICATION OF LIFE • Organisms can be classified into groups based on morphological, behavioral, and evolutionary relationships • Classifying organisms is important to scientists as it provides a framework and a common “language” which enables scientists everywhere to study and understand more about life on Earth • Taxonomy is the science of classification

19. Scientists currently recognize 3 Domains

20. The Linnean system of classificationDomain, Kingdom, Phylum, Class, Order, Family, Genus, Species Category Domestic cat Domain Eucarya Kingdom Animalia (animals) Phylum/Division Chordata (chordates) Class Mammalia (mammals) Order Carnivoria (carnivores) Family Felidae (cats) GenusFelis Speciessilvestris

21. REVIEW QUESTIONS • 1. A horse and a donkey may interbreed with each other and produce offspring. The offspring are generally sterile, however, because the horse and the donkey are of different • a. orders • b. kingdoms • c. species • d. phyla • 2. The following illustration represents a phylogenetic tree which includes several different organisms. Based upon this diagram, which of the following groups of organisms have the closest evolutionary relationship? • a. mammals and lizards • b. mammals and frogs • c. lungfish and frogs • d. lizards and snakes

22. 3. Which of the following would provide the best data for determining the phylogeny (evolutionary history) of three very closely related species? a. fossil records b. comparison of anatomical structures c. comparisons of their scientific names d. comparison of DNA sequences 4. Which of the following characteristics did Linnaeus use to classify organisms? a. DNA similarities b. Environments in which the organisms lived c. The color of the fur, skin, or feathers d. Shape, size and structure

23. The extinction of species can be a natural process • Extinctions occur “often” in evolutionary history • Scientists estimate that more than 90% of the species that have lived on earth are probably extinct • Most extinctions occur due to selective nature of the species • The fossil record provides evidence that background extinctions regularly occur throughout time

24. MASS EXTINCTIONS • Scientific studies show another type of extinction in which massive numbers of species become extinct in a short period of time • These are called mass extinctions • There are 5 recognizable periods of mass extinction in the earth’s history • There are several theories as to the cause of the mass extinctions, most of which hypothesize that major climatic and environmental changes occurred globally

25. 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.

26. MORE ON EXTINCTION • The extinction of a species can occur through the process of evolution • Extinction by natural causes may be due either to actual death of a species or due to evolution of the species into one or more different species • Evidence from the fossil records substantiates that many species have become extinct and new species have developed over time • Many scientists believe that Earth may be in a 6th mass extinction phase, as many species are going extinct every day

27. REVIEW QUESTIONS • 1. Which of the following has NOT been implicated as contributing to mass extinctions? • a. volcano eruptions • b. changes in ocean water level • c. major hurricanes • d. asteroid impact • 2. What percent of species that have ever lived on earth are probably extinct? • a. 28% • b. 52% • c. 77% • d. 90% • 3. Which of the following does NOT likely contribute to background extinctions? • a. evolution through natural selection • b. destruction of a habitat due to natural or human cause • c. interbreeding between species • d. changes in local environmental conditions

28. 4. The following diagram illustrates numbers of extinctions that have occurred over time. What is the highest rate of background extinction indicated in this diagram? a. 10 families per million years b. 7 families per million years c. 17 families per million years d. 5 families per million years