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CHAPTER 4

CHAPTER 4. Biodiversity. The variety of the earth’s species, the genes they contain, the ecosystems where they live and the energy flow and nutrient cycle that sustain life. Is a vital renewable resource. 1.8 million species have been identified.

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CHAPTER 4

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  1. CHAPTER 4

  2. Biodiversity • The variety of the earth’s species, the genes they contain, the ecosystems where they live and the energy flow and nutrient cycle that sustain life. • Is a vital renewable resource. • 1.8 million species have been identified. • Thousands of new species are identified each year. • Typically, higher biodiversity = more stable system.

  3. Biodiversity Divided into: • Genetic diversity - diversity of genes within a species. There is a genetic variability among the populations and the individuals of the same species. • Species diversity - diversity among species in an ecosystem. Ex - rainforest • Ecosystem diversity - the variety of ecosystems on Earth • Functional diversity – the variety of processes occurring in an ecosystem.

  4. Most species are insects!

  5. Measuring Biodiversity For a geographic area must consider: • Species evenness – count of the number of different organisms within a species • Species richness – the number of different species We sampled two fields for wildflowers. The first field has 300 daisies, 335 dandelions and 365 buttercups. The second field has 20 daisies, 49 dandelions and 931 buttercups. Both samples have the same richness (3 species) and the same total number of individuals (1000). However, the first sample has more evenness than the second. • A community dominated by one or two species is considered to be less diverse than one in which several different species have a similar abundance.

  6. Variations in Species Richness and Species Evenness Richness Evenness

  7. Biodiversity is important part of the earth’s natural capital • Supplies us with food, wood, fibers, energy and medicines • Preserves the quality of air and water and maintains the quality of soil • Helps us dispose of wastes and to control pest populations. • Biodiversity helps sustain life on earth

  8. Natural Capital: Nature’s Pharmacy

  9. Shannons's diversity index - accounts for both abundance and evenness of the species present • H = -Σ Pi(lnPi)  where Pi is the proportion of each species in the sample H ranges from 0 – 4.6. 0 = every species is the same; no biodiversity 4.6 = evenly distributed species; high biodiversity

  10. Species-Rich Ecosystems Tend to Be Productive and Sustainable Species richness seems to increase productivity and stability or sustainability How much species richness is needed is debatable

  11. Species Diversity • Species diversity • Species richness • Species evenness • Diversity varies with geographical location • Most species-rich communities (highest in the tropics and less as you move from the equator toward the poles) • Tropical rain forests • Coral reefs • Ocean bottom zone • Large tropical lakes

  12. Where Do Species Come From? Concept : The scientific theory of evolution explains how life on earth changes over time through changes in the genes of populations. Concept : Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (natural selection).

  13. Biological Evolution • Changes in the genetic makeup of a population of a species, not an individual, in successive generations. • Charles Darwin and Alfred Russel Wallace independently proposed the idea of natural selection as a mechanism for biological evolution. (1858) • Darwin gathered and published his evidence in his book, On the Origin of Species by Means of Natural Selection.

  14. Observed that organisms constantly struggle to survive. • Individuals in a population with specific advantageous traits are more likely to survive, reproduce and have offspring with similar survival skills. • Be sure to see the power point on Darwin on my website!

  15. Natural selection occurs when some individuals of a population have genetically based traits that enhance their ability to survive and produce offspring with the same traits. • This change in genetic characteristics of a population from generation to generation is known as evolution.

  16. Life has evolved into 6 major kingdoms. The phylogeny of life

  17. The Genetic Makeup of a Population Can Change Populations (not individuals) evolve by becoming genetically different Genetic variations First step in biological evolution Occurs through mutations in reproductive cells which involve random changes in the structure or number of DNA molecules in a cell

  18. Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring Natural selection: acts on individuals Second step in biological evolution When individuals of a population have genetically based traits that enhance their ability to survive Adaptations may lead to differential reproduction (those with the trait leave more offspring than the other members) Ex: thick fur, chemical tolerance When environmental conditions change, populations Adapt Migrate Become extinct

  19. Natural selection can be attributed to changes in the gene pool in a population. • Traits in a species change in response to selection pressures • Physiological stress (temp, humidity) • predation • Competition • Chance (mutations) • The ultimate source of variation in genes is mutations!

  20. Evolution by Natural Selection

  21. Natural selection

  22. Population Genetics • A population consists of a gene pool – all the various genes in a species. • Alleles are different forms of one gene. • Evolution – change in a gene pool over time, essentially a change in types of alleles.

  23. 4 major evolutionary forces alter population gene pools: • Mutations – changes in DNA, slow rate, most important • Emigration/immigration (gene flow) – movement of genes into or out of the pop. • Random genetic drift – unpredictable variations change the pool • Natural selection – one phenotype has more reproductive success Phenotype- physical representation of the genotype (gene)

  24. Adaptation Through Natural Selection Has Limits • A change in environmental conditions can lead to an adaptation only for genetic traits already in the gene pool. • A population’s ability to adapt may be limited by its reproductive capacity.

  25. Divergent evolution- organisms become less alike but have a common ancestor (ex: human arm and dog’s foreleg) • Convergent evolution – lack a common ancestor, but are similar (ex: shark and dolphin) • Vestigial organs- organs that were once useful in an animal’s evolutionary past, but now has no apparent nor predictable function (ex: wings on flightless birds, whales hind leg bones, wisdom teeth) Observations of vestigial organs helped Darwin with his theory of natural selection.

  26. Adaptive radiation – development of many species from a single one.. (ex: Darwin’s finches, Hawaiian silversword plant- 28 species, came from sunflower)

  27. Why are Humans a Successful Species? • Strong, opposable thumbs • An ability to walk upright • A complex brain

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