2. BIODIVERSITY, SPECIES INTERACTIONS, and POPULATION CONTROL! BIODIVERSITY, SPECIES INTERACTIONS, and POPULATION CONTROL!

3. How do Species Interact?  5 major ways!  Interspecific Competition  Predation  Parasitism  Mutualism  Commensalism  Interactions help limit population size. These interactions influence abilities of interacting species to survive and reproduce; thus serving as agents of natural selection.

4. Competition Competition  Each species has a niche.(some are generalists with broad niches, others are specialists with narrow niches)  When niches overlap, competition occurs. No two species can share a niche for very long (competitive exclusion principle)

5. PREDATORS! PREDATORS!

6.  In predation, a member of one species feeds directly upon all or part of another living organism as part of a food web.  Herbivores, carnivores, and omnivores are predators. (Decomposers and detritovores are not)  See page 102 to read about how predators catch prey and how prey tries to keep from being eaten. Vivid reading!

7. PREY!! PREDATOR!! PREY!! PREDATOR!!

8. Read about Kelp! p. 104

9. PARASITISM! (Feeds on the body or energy of another organism)

10. MUTUALISM! Both Benefit!

11. Commensalism! Benefits one, but doesn’t help or harm other. (bromeliads and tree….whale and barnacle)

12. Reduce Competition by Resource Partioning!  Species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places.  Examples are warblers and honey creepers.

13. We all live in the same tree! But we eat different things in different places in our tree!

14. Limits to Population Growth!!  Populations differ in factors such as distribution, numbers, age structure, and density.  Age structure(number of individuals in different age groups)  Density(number of individuals in a certain space)  Population dynamics is a study of how these characteristics of populations change in response to environmental conditions.(Temperature, presence of disease or harmful chemicals, resource availability, and arrival or disappearance of a competitor)

15. Snow bird to beach bunny! (NY to FLA) (Mice leave when cat moves in)

17. CLUMPS and PATCHES  Most populations live in clumps or patches. (Desert vegetation near water, wolf packs, fish schools, bird flocks, herds)  Groups cluster where resources are  Searching in groups is better than alone  Groups protected more from predators  Better hunting in packs  Group together for mating and raising young.  The Living World is Clumpy and Patchy!!

18. We are happy! We Clump!

19. Uniform Random Dispersion Dispersion

20. 4 Variables Govern Population Size!  Births(come in)  Deaths(go out)  Immigration(move in)  Emigration(move out)  (Age structure is important in determining if a population is likely to grow or decrease. )

21. Biotic Potential  Biotic potential is the capacity for populations to grow under ideal conditions.  Huge animals like elephants and whales have low biotic potential.  Bacteria and insects have high biotic potential

22.  The INTRINSIC RATE OF INCREASE (r) is the rate at which the population of a species would grow if it had unlimited resources.  Populations with high (r) have individuals that reproduce early, have short generation times, reproduce many times, and have many offspring each time they reproduce.(Example:Bacteria)  No population can grow indefinitely because of limiting factors such as light, water, space, and food, or exposure to competitors, predators, or disease. THERE ARE ALWAYS LIMITS TO POPULATION GROWTH)

23.  Environmental Resistance is the combination of all factors that act to limit population growth.  Together, biotic potential and environmental resistance determine CARRYING CAPACITY (K): the maximum population of a given species that a particular habitat can sustain indefinitely without being degraded.  The growth rate of a population decreases as its size nears the carrying capacity of its environment.

24. Food and Space are getting scarce  Carrying capacity reached. Fewer fishes.

25.  EXPONENTIAL GROWTH: starts slowly, accelerates quickly. (Few limitations on growth. Many resources.) This is shown on graph as a J-shaped curve.  LOGISTIC GROWTH: involves rapid exponential growth followed by a steady decrease until population levels off. (Dwindling resources) This is shown as an S-shaped curve on a graph.

26.  Changes in the population of a keystone species such as the southern sea otter or the American alligator can alter the species composition of an ecosystem.  Example: Decline in sea otters caused a decline in species dependent on them, such as giant kelp. This reduced species diversity in kelp forests and altered its functional biodiversity by upsetting food webs and reducing energy flows and nutrient cycles.

27. I am endangered.  Read about my plight on p. 110

28. I EAT SEA OTTERS!!

29. Parasites in my tummy make sea otters sick!!

30. Moving on…..  Sometimes a population grows so fast that it doesn’t transition from exponential to logistic growth smoothly….alas, it temporarily OVERSHOOTS, or exceeds the carrying capacity of the environment. (Caused by reproductive time lag)  Then the population suffers a DIEBACK, or CRASH, unless the excess individuals move to new resources or switch to new resources.

31. REPRODUCTIVE PATTERNS  R-SELECTED SPECIES: species with a capacity for a high rate of population increase (r).  Have many small offspring. Little parental care.  Big numbers of babies offset large losses. Reproduce and disperse rapidly when conditions are right.  Opportunistic.

32. We take advantage!!

33.  K-SELECTED SPECIES: These are competitor species.  Reproduce later in life. Have fewer offspring. Born larger. Cared for by parent.  More competitive for resources.  Follow logistic growth curve.  Can be prone to extinction, especially if heavily hunted.

34. We are “K-Select”

35. r-select K-select on the farm!!

36. Genetic Diversity in Small Populations! It can be lost!  Founder Effect: a few individuals in a population colonize a new habitat that is geographically isolated from the rest of the population.  These foxes live in isolated areas.

37.  Demographic bottleneck: Only a few individuals survive a catastrophe. Lack of genetic diversity may limit their ability to rebuild population.   Even if population increases, lack of genetic diversity may lead to an increase of genetic diseases.

38.  Genetic Drift: Random changes in gene frequency may lead to unequal reproductive success.  Some individuals may breed more, so their genes dominate. This could help or hinder the population’s survival.  This is similar to founder effect or bottleneck.  Example: polydactyly in Old Order Amish.

39.  Inbreeding: Occurs when individuals in a small population mate with one another.  Can occur through bottleneck.  Increases frequency of defective genes.  Example: Hapsburg royal family

40. POPULATION DENSITY  Population Density: the number of individuals in a population found in a certain area.  Density-dependent population controls include predation, parasitism, infectious disease, and competition. These have a greater effect as population density increases.  Density-independent population controls are not dependent on population density: severe freeze, floods, hurricanes, fire, pollution, habitat destruction.

41. 4 Patterns of Variation in Population Size  STABLE: fluctuates only slightly above or below carrying capacity.  Example: tropical rainforest species

42.  IRRUPTIVE: explodes with a high peak, then crash! Gets stable or goes low.  Example: Temperate climate insects

43.  CYCLIC: cyclic fluctuations or boom and bust cycles.  Examples: lemmings, lynx and hare.  Top-down regulation is through predation.  Bottom-up regulation is by scarcity of resources.

44.  IRREGULAR: No recurring pattern. Chaos, catastrophe, severe weather.  Examples: Bubonic plague, potato famine, AIDS

45. YAY!! TECHNOLOGY!!  Technological, social, and other cultural changes have extended the earth’s carrying capacity for the human species.

46. Read about the White- Tailed Deer. pp.114-15