Evolution and Biodiversity

1. Evolution and Biodiversity G. Tyler Miller’s Living in the Environment 14th Edition Chapter 5

2. Key Concepts • Origins of life • Evolution and Evolutionary processes • Ecological niches • Species formation • Species extinction

3. Origins and Early Evolution of Life OBJ 5.1 • Chemical evolution: • organic molecules, biopolymers, chemical reactions • Biological evolution • single-celled prokaryote  single-celled eukaryote  • multicellular organism Fig. 5-2 p. 88

4. MICROEVOLUTION OBJ 5.2 Small genetic changes that occur in a population • MECHANISM OF MICROEVOLUTION • mutation • migration • genetic drift • natural selection

5. Imagine that you observe an increase in the frequency of brown coloration genes and a decrease in the frequency of green coloration genes in a beetle population. Which of these mechanisms caused the change:

6. MUTATIONS DEFINITION: RANDOM CHANGES IN THE STRUCTURE OR # OF DNA MOLECULES IN A CELL THAT CAN BE INHERITED. Some “green genes” randomly mutated to “brown genes” (although since any particular mutation is rare, this process alone cannot account for a big change in allele frequency over one generation).

7. MIGRATIONSGENE FLOW Some beetles with brown genes immigrated from another population, or some beetles carrying green genes emigrated.

8. GENETIC DRIFT When the beetles reproduced, just by random luck more brown genes than green genes ended up in the offspring. In the diagram at right, brown genes occur slightly more frequently in the offspring (29%) than in the parent generation (25%).

9. NATURAL SELECTION Beetles with brown genes escaped predation and survived to reproduce more frequently than beetles with green genes, so that more brown genes got into the next generation.

10. Natural Selection OBJ 5.3 • Differential reproduction • enable individuals with the favorable trait to leave more offspring than other members of the population • Adaptive trait or adaptation • any heritable trait that enables organisms to better • survive and reproduce under prevailing environmental • conditions • Coevolution • when populations of 2 different species interact over a long period of time, changes in gene pool of one can result in change of gene pool of another

12. MACROEVOLUTION long term, large-scale evolutionary changes through which new species form from ancestral species and other species are lost through extinction

13. a species way of life or functional role in a community or ecosystem & involves everything that affects its survival and reproduction What is the niche? set of conditions within which an organism can maintain a viable population multi-dimensional with as many dimensions as their are limiting conditions ecological niche light intensity okay temperature salinity

14. Ecological Niches and Adaptation Fig. 5-4 p. 91

15. Broad and Narrow Niches OBJ 5.4 • Generalist species • - broad niches • - live in variety of places • - eat variety of foods • - wide range of tolerance Refer to Spotlight p. 92 • Specialist species • narrow niche • Live in specific habitat • Use only few type of food • Tolerate narrow range of environmental conditions

16. OBJ 5.5 Fundamental niche depends on physical (abiotic) conditions. Realized niche depends on biotic as well as abiotic conditions. What is the realized niche of each barnacle? What is the fundamental niche of each?

17. How can we determine the realized niche of each barnacle? Where do they grow when allowed to compete? Balanus and Chthamalus growth rate Balanus realized niche Chthamalus realized niche low middle high Location in intertidal zone

18. How can we determine the fundamental niche of each barnacle? Removal experiments – remove each species and see where the other grows Balanus alone Balanus fundamental niche growth rate Chthamalus alone Chthamalus fundamental niche low middle high Location in intertidal zone

19. The niche of a species may contract in the presence of a competitor species. This phenomenon leads to resource (niche) partitioning and coexistence among functionally similar species. The narrower niche resulting from competition is called the realized niche. What happens if the competitor is removed?

20. EVOLUTION MISCONCEPTIONS OBJ 5.6 • SURVIVAL OF THE FITTEST = SURVIVAL OF STRONGEST • Fitness is measure of reproductive success NOT strength • fittest individuals leave the most offspring • EVOLUTION INVOLVES GRAND PLAN OF NATURE WHERE SPECIES BECOME MORE PERFECTLY ADAPTED • there is no plan or goal

21. SPECIATION • The process in which 2 species arise from one. • new species formed when some members of a population can no longer breed with other members to produce fertile offspring

22. GEOGRAPHIC ISOLATION OBJ 5.7 DIFFERENT GROUPS OF THE SAME POPULATION BECOME PHYSICALLY ISOLATED FROM ONE ANOTHER FOR LONG PERIODS Fig. 5-7 p. 94

23. Reproductive Isolation With or Without Geographic Isolation Allopatric speciation occurs when geographic isolation creates a reproductive barrier (an extrinsic mechanism). Sympatric speciation occurs when a reproductive barrier is created by something other than geographic isolation (intrinsic mechanisms).

24. Allopatric Speciation White-tailed antelope squirrel Harris’ antelope squirrel Two species of ground squirrel are postulated to have descended from a common ancestral population that was separated by formation of the Grand Canyon.

25. White-tailed antelope squirrel Harris’ antelope squirrel Intrinsic Reproductive Isolating Mechanisms Are Always Required for Speciation changes to organisms that prevent interbreeding In allopatric speciation, intrinsic mechanisms come into play once populations are physically separated. In sympatric speciation, intrinsic mechanisms are the only ones involved.

26. (different habits within an overlapping range) Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation

27. Courtship rituals, like these, are critical for mating within a species, but ineffective for attracting members of other species. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation

28. Behavioral Isolation Mechanisms Courtship rituals, like these, are critical for mating within a species, but ineffective for attracting members of other species.

29. Many Intrinsic Reproductive Isolating Mechanisms Drive Speciation

30. Current Status of Biodiversity 1.4 million described species, possibly 10 million in total Background extinction rate – rate of species loss in the absence of human activities fossil record: species survive 1-10 million years one year: one species has a 1 in 1-10 million chance of going extinct total: 1 extinction per year OBJ 5.8

31. Species Come and Go Best estimates from the fossil record indicate that greater than 99% of species that have exited are now extinct. A typical “lifetime” for a species is about 1 million years.

32. Mass extinction – loss of large number of species usually due to catastrophic volcano or meteor impact very rare (5 times in 3 billion years) Current rate of extinction???

33. Mass Extinctions Are a Fact of Life

34. Are We Now Causing a Mass Extinction?

35. Causes of species declines Habitat destruction and fragmentation Introduced species Exploitation and overharvesting Pollution Climate change OBJ 5.9

36. USA

37. Habitat destruction and fragmentation Fragmentation – disruption of extensive habitats into small, isolated patches

39. Introduced species Humans are constantly moving species between continents, islands deliberate or accidental Most serious impacts on islands low species diversity few native predators animals lack anti-predator defenses, resistance to diseases

40. Exploitation and overharvest Direct exploitation for food overfishing “bycatch” in fisheries – killing non-target species (birds, marine mammals) “bush meat” – harvest of wild animals for food can be sustainable, but often not threatens many large mammals, primates

42. Pollution Most important for aquatic systems chemical pollutants acid precipitation Bioaccumulation – process by which toxin concentrations increase in living tissues concentrations increase through the food chain

44. Climate change

46. FUTURE OF EVOLUTION Artificial Selection changes genetic characteristics of a population select 1 or more traits, then selectively breed results in many breeds or hybrids of same species OBJ 5.10

47. GENETIC ENGINEERINGaka gene splicing • techniques for isolating, modifying, multiplying, • & recombining genes from different organisms • transfer genes b/w species • EX: fish species gene  tomato or strawberry • result in GMO (genetically modified organisms)