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Brainstorm You and the person next to you will list 3 examples of….. Abiotic and biotic factors that affect population growth and decrease in size.

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Presentation on theme: "Brainstorm You and the person next to you will list 3 examples of….. Abiotic and biotic factors that affect population growth and decrease in size."— Presentation transcript:

1 Brainstorm You and the person next to you will list 3 examples of….. Abiotic and biotic factors that affect population growth and decrease in size.

2 Chapter 9 Population Unit

3 Population Dynamics Studying how populations change in size, density, age distribution, and population distribution. Size: number of individuals Density: how many are in a certain area Age distribution: proportion of each age group Population distribution: how the organisms arrange themselves in their habitat

4 Population Distribution Clumping: Most common. Safety in numbers, social interaction, mating and caring for young, resources are clumped Uniform: Not as common. Used because of scarcity of resources Random: Quite rare. Can be hard to determine between truly random or largely clumpy Most common.

5 What goes up must come down Increases in population: through birth or immigration Decreases in population: through death or emigration. Change in Population Births + Immigration Deaths + Emigration Note: You should know difference between Immigration & Emigration!

6 Age Structure What is expected to happen if a large % of the population is under the age of 10? What is expected to happen if a large % of the population is over the age of 65? What is expected to happen if there is an equal distribution in age? Growth will remain stable, then increase in 10-20 years Growth will decrease Growth remain stable

7 What stage are you? Prereproductive stage: Those not through puberty; reproductively immature. Reproductive stage: Those who are capable of reproduction Postreproductive stage: Organisms that are too old to reproduce. Note: while males are capable of reproduction longer, survival of the fittest can prevent them from breeding once they are too old.

8 Old Bio Stuff Abiotic vs. Biotic Factors That limit population growth Not living Sunlight Temperature Climate Chemical environment Living factors Reproduction rates Food supply Habitat Resistance to disease Ability to adapt to change Abiotic Biotic

9 POPULATION SIZE Growth factors (biotic potential) Favorable light Favorable temperature Favorable chemical environment (optimal level of critical nutrients) Abiotic Biotic High reproductive rate Generalized niche Adequate food supply Suitable habitat Ability to compete for resources Ability to hide from or defend against predators Ability to resist diseases and parasites Ability to migrate and live in other habitats Ability to adapt to environmental change Decrease factors (environmental resistance) Too much or too little light Temperature too high or too low Unfavorable chemical environment (too much or too little of critical nutrients) Abiotic Biotic Low reproductive rate Specialized niche Inadequate food supply Unsuitable or destroyed habitat Too many competitors Insufficient ability to hide from or defend against predators Inability to resist diseases and parasites Inability to migrate and live in other habitats Inability to adapt to environmental change Biotic potential = growth Environmental resistance = decrease

10 A population will increase if…. A) Natality decreases B) Mortality increases C) Biotic potential increases D) The environmental resistance increases

11 A population will increase if…. A) Natality decreases B) Mortality increases C) Biotic potential increases D) The environmental resistance increases

12 Favorable light Favorable temperature Favorable chemical environment (optimal level of critical nutrients) Abiotic Biotic High reproductive rate Generalized niche Adequate food supply Suitable habitat Ability to compete for resources Ability to hide from or defend against predators Ability to resist diseases and parasites Ability to migrate and live in other habitats Ability to adapt to environmental change Any of these would take place for answer C. Biotic potential = growth

13 Exponential or Logistic Growth Curve? Boom and Bust Boom then stable

14 Logistic Growth Will see exponential growth at first introduction to new environment. Video to follow this lecture. Then, growth will be limited by environmental factors and will follow carrying capacity S shaped Population size (N) Time (t) Carrying capacity (K) Environmental resistance Biotic potential Exponential growth

15 Clearer view of J and S

16 Going up… Intrinsic rate of increase (r) is the rate the population would grow if it had unlimited resources. Can be seen as the boom of the population. r species: reproduce early in life, reproduce often, have many offspring each time.

17 Coming down… Overshoot occurs when the population booms and is too great for the resources to support Overshoot is followed by dieback, or the sudden decrease in population Reproductive time lag: the amount of time it takes for the birth rate to fall and death rate to rise. If the time lag is too long, environmental damage can occur which further limits the carrying capacity.

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19 Population Graphs Number of individuals Time (b) Irregular

20 Population Graphs Number of individuals Time (a) Stable

21 Population Graphs Number of individuals Time (c) Cyclic

22 Population Graphs Number of individuals Time (d) Irruptive (

23 Oscillations of the Two Populations Over Time

24 Population Density Density-dependent controls: Limits populations that are too high. Examples: competition for food, shelter, water; disease; parasites, predation Density-independent controls: Decreases population regardless of size. Examples: weather, temperature, natural disasters, habitat destruction, chemical changes in the environment

25 Whos in control here? Top-down control: (Predator Controls Prey) –Structure of lower trophic levels depends on effect of consumers at high trophic levels. Bottom-up control: (Prey Controls Predator) – Structure depends on prey availability and nutrient content from low trophic levels Example: Hare population is controlled either by the lynx killing it (top-down) or by large numbers of hare using up their food source (bottom-up)

26 Lets talk about sex… old bio stuff Asexual reproduction: does not require sperm/egg. Mitosis – cell splitting. Bacteria reproduce this way. Only 3% of all species use this form Sexual reproduction: requires sperm/egg, but not necessarily intercourse/copulation Disadvantages: –Males dont give birth –Increased chance of genetic defect/error –Courtship and mating rituals can be complex Advantages: (get your mind out of the gutter!) –Genetic variety/diversity –Parents can divide responsibilities

27 What species are you? Number of individuals Time Carrying capacity K species; experience K selection r species; experience r selection

28 Remember – You are SPECIAL

29 Species Found at bottom of population curve Reproduce early in life Reproduce frequently Large numbers of offspring Little to no parental care Boom and bust populations Examples: –Frogs –Cockroach –Dandelions –Mice –Most insects Found at top of population curve Reproduce later in life Reproduce less frequently Have less offspring at one time Lower infant mortality Logistic graph (stable at top) Examples: –Humans –Elephants –Whales –Long-living plants (oaks, rain forest trees) r-selected SpeciesK-selected Species

30 R-selected Species or K-selected species?

31 R-selected Species or K-selected species?

32 R-selected Species or K-selected species?

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34 R-selected Species or K-selected species?

35 R-selected Species or K-selected species?

36 R-selected Species or K-selected species? HINT: The Capybara is the largest rodent in the world

37 Survivorship Curves Early loss: high infant mortality (fish, frogs) Constant loss: death rate even among all ages (song birds) Late loss: low infant mortality (humans, elephants) Percentage surviving (log scale) 100 10 1 0 Age Early loss Constant loss Late loss

38 Isolation isnt best… Problems when small, isolated populations exist. –Founder effect: small group is geographically isolated. May not have the genetic diversity to survive (coloring, fur cover, etc) –Demographic bottleneck: only a few surviving individuals may not have the genetic diversity to rebuild the population –Genetic drift: some individuals breed more and dominate the gene pool (wolves) –Inbreeding: related individuals in an area mate. Can increase genetic defects.

39 Tying in a few things from Chapter 1

40 Oops! I did it again… Past mistakes that need to be stopped: –Reducing biodiversity by destroying, fragmenting and degrading habitats

41 Oops! I did it again… Past mistakes that need to be stopped: –Reducing biodiversity by simplifying natural ecosystems (monocultures – one type)

42 Oops! I did it again… Past mistakes that need to be stopped: –Unintentional strengthening of pest species and anti-biotic resistant bacteria

43 Oops! I did it again… Past mistakes that need to be stopped: –Elimination of natural predators (wolves, cougars, buffalo, eagles)

44 Oops! I did it again… Past mistakes that need to be stopped: –Over-harvesting renewable resources

45 Oops! I did it again… Past mistakes that need to be stopped: –Interfering with natural cycles in natural

46 Oops! I did it again… Past mistakes that need to be stopped: –Over dependence on fossil fuels

47 4 Guidelines for a Sustainable Future Our lives and economies are dependant on the earth and sun. They dont depend on us. Everything is interconnected. You cant change only one thing in nature We cannot sustain our civilization if we deplete the natural capital. We must live off the biological interest of that capital.

48 PRINCIPLES OF SUSTAINABILITY Population Control Solar Energy Biodiversity Nutrient Recycling


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