Biodiversity, Species Interactions, and Population Control

1. Biodiversity, Species Interactions, and Population Control Chapter 5

2. Biodiversity, Species Interactions, and Population Control Chapter 5 Part 1: Species Interactions

3. Review! • What is evolution? • Change in a species over time (many generations!) • What is natural selection? • Pressures of environment ‘select’ genes that survive to produce more offspring • What is an adaptation? • Trait that improves chances for survival and reproduction

4. Coevolution • The process by which two species evolve in response to changes in each other over time • Sometimes organisms that are closely connected to one another by ecological interactions evolve together.

5. Coevolution: A Langohrfledermaus Bat Hunting a Moth

6. Species Interact in Five Major Ways • Interspecific Competition • Predation • Parasitism • Mutualism • Commensalism

7. Most Species Compete with One Another for Certain Resources • Competition • When two species compete, their niches overlap • Competitive exclusion principle – no two species can occupy exactly the same ecological niche for very long • Both species suffer harm • Migration or predation will ultimately occur

8. Some Species Evolve Ways to Share Resources • Resource partitioning – species evolve to reduce niche overlap • Use shared resources at different • Times • Places • Ways

9. Specialist Species of Honeycreepers

10. Sharing the Wealth: Resource Partitioning

11. Predator or Prey? • Predation – act of one organism eating another organism • Predator – organism that does the eating • Prey – organism that gets eaten

12. Most Consumer Species Feed on Live Organisms of Other Species • Predators may capture prey by: • Walking • Swimming • Flying • Pursuit and ambush • Camouflage • Chemical warfare

13. Most Consumer Species Feed on Live Organisms of Other Species • Prey may avoid capture by • Camouflage • Chemical warfare • Warning coloration • Mimicry • Deceptive looks • Deceptive behavior

14. Important lesson to remember: • If an organism is small and beautiful… it is probably poisonous. • If it is strikingly beautiful and easy to catch…it is probably deadly.

15. Predation: Population Control • Cyclic fluctuations, boom-and-bust cycles • Top-down population regulation • Controlled by predation • Bottom-up population regulation • Controlled by scarcity of one or more resources

16. Your Turn! • Predator Prey Relationships

17. Video Clip • Orca Training Session • 22:42 to 31:00

18. Mutualism: Clownfish & sea anemone • Both organisms derive mutual benefit • Intimate and obligatory • Neither can survive for long periods without the other

19. Mutualism: Oxpeckers Clean Rhinoceros; Anemones Protect and Feed Clownfish

20. Parasitism: Tapeworm and Humans • Parasite lives on or in the host and benefits at the expense of the host

21. Parasitism: Tree with Parasitic Mistletoe, Trout with Blood-Sucking Sea Lampreys

22. Commensalism: Flatworms and horseshoe crabs • Only one member benefits • sharing space, defense, shelter, food • Flatworms that live on the gills of horseshoe crabs obtain food from the host, but do not negatively affect the host

23. Commensalism: Bromiliad Roots on Tree Trunk Without Harming Tree

24. Your Turn! • http://www.pbs.org/wnet/nature/lessons/symbiotic-strategies/video-segments/1496/ • Ecological Relationships • Predation • Competition • Commensalism • Mutualism • Parasitism

25. Biodiversity, Species Interactions, and Population Control Chapter 5 Part 2: Population Dynamics

26. Populations Have Certain Characteristics • Population dynamics – study of how characteristics of a population changes in response to changes in the environmental conditions • Populations differ in • Distribution • Numbers • Age structure

27. Density • Number of individuals of a population in a given area

28. Distribution Patterns • Random • Independent of other organisms • No habitat preference

29. Distribution Patterns • Uniform • Even spacing • Evidence for intra-specific competition (among other sea otters)

30. Distribution Patterns • Clumped • Organisms tend to be together • Habitat preference • Behavioral preference such as herding • Most common!

31. Why clumping? • Species tend to cluster where resources are available • Protects some animals from predators • Packs allow some to get prey • Temporary groups for mating and caring for young

32. Populations Can Grow, Shrink, or Remain Stable • Population size governed by • Births • Deaths • Immigration • Emigration • Population change = (births + immigration) – (deaths + emigration)

33. Populations Can Grow, Shrink, or Remain Stable • Age structure – number of individuals in a given age class • Pre-reproductive age • Reproductive age • Post-reproductive age

34. Density Dependent Limiting Factors • Operates more strongly when a population is large and overcrowded • Predation – more prey organisms – predator numbers will increase

35. Density Dependent Limiting Factors • Parasitism – crowding helps parasites travel from one host to another • Crowding – higher levels of stress (direct influence on immune system)

36. Density Dependent Limiting Factors • Competition • Intraspecific – members of the SAME species compete • Interspecific – competition between DIFFERENT species

37. Density-Independent Limiting Factors • Will affect population regardless of its size • Natural Disasters • Forest fires • Floods • Earthquake • Oil Spill

38. Genetic Diversity Can Affect the Size of Small Populations • Minimum viable population size – number of individuals endangered species need for long-term survival • Founder effect • Demographic bottleneck • Genetic drift • Inbreeding

39. Case Study: Exploding White-Tailed Deer Population in the U.S. • 1900: deer habitat destruction and uncontrolled hunting • 1920s–1930s: laws to protect the deer • Current population explosion for deer • Lyme disease • Deer-vehicle accidents • Eating garden plants and shrubs • Ways to control the deer population