Natural Selection and Species Interactions

1. Natural Selection and Species Interactions “Nature has given women so much power….” - Samuel Johnson

2. The Great Leap Forward • Starting in 1958, Mao Zedong, leader of the Communist Party of China, initiated a series of policies to transform the country into a modern, industrialized, communist society. • One of the first actions taken was known as the Four Pests Campaign. • This campaign sought to eliminate rats, flies, mosquitoes, and sparrows.

3. The Four Pests Campaign • Masses of people were mobilized to eradicate the Eurasian Tree Sparrow. • Tactics included: • Banging pots and pans, preventing the birds from landing, until they were exhausted. • Tearing down nests. • Shooting them from the sky using guns and sling shots. “Everyone come and fight sparrows.”

4. Unintended Consequences • The sparrows were hunted because they ate grain seeds; reducing crop yields. • By April of 1960, Chinese leaders came to realize that the sparrows also ate a large number of pest insects, including locusts.

5. Unintended Consequences • The government made a series of other poor agricultural decisions at this time, including: • Ordering farmers to increase the density of their planting by 6 times, believing that the same species of plant would compete with itself. • Deeper plowing of the soil, which brought up sand and rocks instead of more topsoil.

6. The Great Famine • The locust plague, overplanting, and overplowing combined with a severe drought. • The number of victims is unknown, but estimated between 20-43 million.

7. Ecosystems: Everything is Connected • An ecosystem is all of the organisms living in an area. • Components of an ecosystem: • Biotic Factors – Living and once living parts of an ecosystem. • Ex: Plants, animals, dead matter, waste • Abiotic Factors – Nonliving parts of an ecosystem. • Ex: Water, rocks, light

8. Organization of Life and the Environment • Organism – An individual living thing. • Species – A group of organisms able to breed and fertile offspring. • Population - All members of a species that live in the same area at the same time. • Biological Community - All populations living and interacting in an area. • Ecosystem - A biological community and its physical environment. • Biosphere – All ecosystems in the entire Earth.

9. Ecosystem Organization

10. What lives where, and why? • Habitat – Where an organism lives • Every organism a range of factors it can survive in. • Ex: Temperature, precipitation, etc. • Critical Factor - Single factor that is the most critical in determining how species are distributed – who lives in what habitat.

11. Tolerance Limits • Tolerance Limits - Minimum and maximum levels beyond which a particular species cannot survive or reproduce.

12. Adaptation • Adaptation – A trait that allows a species to survive more easily and reproduce. • Evolution - Inheritance of specific genetic traits that control adaptations, giving a species an advantage in an environment.

13. Natural Selection • Natural Selection - Describes process where better competitors survive and reproduce more successfully. • Caused by: • Random mutations – Changes in DNA are usually bad, but can be beneficial. • Selective pressure – Limited resources mean only the best competitors survive. • Sexual selection – Females choose a mate based on certain characteristics.

14. Natural Selection

15. Artificial Selection • The selective breeding of organisms by humans for specific characteristics.

16. Origin of Life Modern humans (Homo sapiens) appear about 2 seconds before midnight Recorded human history begins 1/4 second before midnight Origin of life (3.6–3.8 billion years ago) Fig. 4-3, p. 66

17. Evidence of Evolution • Physical Similarities • Most animals have similar bones in their limbs (fins, arms, wings) • Comparing DNA • Vestigial Structures • Still exist in the body but are no longer needed • Ex: Appendix, wisdom teeth

18. Factors Exerting Selective Pressure • Physiological stress due to inappropriate levels of a critical environmental factor. • Moisture, Light, pH • Predation • Organism is hunted and killed by another • Includes parasites, bacteria, viruses • Competition • Other organisms attempting to use same resources • Luck

19. Speciation • Given enough time, enough mutations occur that a new species develops from an old one. • When are two groups considered a different species? • They cannot or will not interbreed to produce healthy, fertile offspring.

20. Natural Selection

21. Speciation • Divergent - Separation of one species into new species.

22. Speciation • Convergent - Unrelated organisms evolve to look and act alike. • Not related • Caused by living in similar environments

23. Coevolution The process of two species evolving in response to long-term interactions with each other.

24. Same or Different Species?

25. Animal Hybrids or New Species? • More examples…

26. The Taxonomic Naming System • Crayfish • a.k.a. Crawdad • a.k.a. Spiny lobster • a.k.a. Yabby • a.k.a. Crawfish • a.k.a. Creekcrab • a.k.a. Mudbug • We need an internationally accepted name!

27. Scientific Naming System • Based on the classification system. • Includes the organism’s genus and species name. • Genus is capitalized • Species is lower case • The scientific name is written in italics • Scientific name of the crayfish: Procambarus clarkii

28. The Taxonomic Naming System • Divides organisms into different levels of organization. • Kingdom • Phylum • Class • Order • Family • Genus • Species • The more levels two organisms have in common, the more related.

30. How related are they? Canis lupus lupus European Wolf Canis familiaris Domesticated dog

31. How related are they? Archocentrus nigrofasciatus Convict Cichlid Corvus splendens House Crow

32. Phylogenetic Tree • Also known as a “tree of life”. • Organisms are grouped and classified based on three characteristics: • Physical characteristics • DNA • Behavioral characteristics • Mating rituals, territorial, aggression, etc. • The more of these characteristics two organisms have in common, the more closely related they areaccording to evolution.

33. Phylogenetic Tree of Life • From left to right: • Orangutan • Gorilla • Human • Chimpanzee • Bonobo

34. Ecological Niche • Habitat - Set of environmental conditions in which a particular organism lives. • Ecological Niche • Description of role played by a species in a biological community.

35. Specific Types of Niches • Opportunistic Species - Quickly appear when any opening in an ecosystem arises. • Many weeds. • Pioneer Species – Able to quickly colonize new ground where nothing else is growing.

36. Types of Niches • Keystone Species - A species whose impact on its ecosystem is especially large and influential.

37. SPECIES INTERACTIONS • Predator-Prey • Any organism that feeds directly on another living organism is termed a predator. • The organism that is eaten is the prey.

38. Competition • Intraspecific - Competition among members of the same species. • Dispersal • Seeds sent far away from parent • Territoriality • Each individual defends part of ecosystem • Resource Partitioning • Adults and larvae eat different foods • Ex: Caterpillars and butterflies • Interspecific - Competition between members of different species.

39. Resource Partitioning • -

40. Symbiosis • Symbiosis - Intimate living together of members of two or more species. • Commensalism - One member benefits while other is neither benefited nor harmed. • Mutualism - Both members benefit. • Parasitism - One member benefits at the expense of other.

41. Example of Symbiosis • Barnacles create homes by attaching themselves to whales. The whales are unaffected.

42. Example of Symbiosis • Clownfish have a mucus coating that allows them to live in sea anemones. Their presence attracts other fish for the anemone to eat.

43. Example of Symbiosis • As bison walk through grass, insects are disturbed and fly away. They are eaten by cowbirds.

44. Example of Symbiosis • Ostriches and gazelles feed next to each other. Ostriches have excellent eyesight, while gazelles have stronger senses of hearing and smell.

45. Example of Symbiosis • Mistletoe extracts water and nutrients from the spruce tree directly.

46. POPULATION DYNAMICS • Population Growth • Studies of population growth are based on the idea of biotic potential. • Biotic Potential - Potential of a population to grow in the absence of limitations.

47. Exponential Growth • Exponential growth is graphed as a J curve. • Carrying Capacity - Number of individuals that can be indefinitely supported in a given area. • Overshoot - When a population surpasses the carrying capacity of its environment. • Dieback – Population experiences a sudden steep drop.

48. Population Oscillations

49. Growth to a Stable Population • Logistic Growth - Growth occurs more slowly as the population approaches carrying capacity due to environmental resistance.

50. Limiting Factors • Environmental Resistance • Any factor that slows the growth of a population. • Density-Dependent Factors – Most likely to affect dense populations. • Disease, Stress, Predation • Density-Independent Factors – Affects dense and diffuse populations evenly. • Changes in climate, natural disasters