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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. Chapter 9. Population Unit. Population Dynamics.

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brainstorm
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.
chapter 9

Chapter 9

Population Unit

population dynamics
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
population distribution
Population Distribution

Clumping: Most common. Safety in numbers, social interaction, mating and caring for young, resources are clumped

Most

common.

Uniform: Not as common. Used because of scarcity of resources

Random: Quite rare. Can be hard to determine between truly random or largely “clumpy”

what goes up must come down
What goes up must come down
  • Increases in population: through birth or immigration
  • Decreases in population: through death or emigration.

Deaths + Emigration

Change in Population

Births + Immigration

Note: You should know difference between Immigration & Emigration!

age structure
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

what stage are you
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.
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

Old Bio StuffAbiotic vs. Biotic FactorsThat limit population growth

Biotic

Abiotic

slide9

POPULATION SIZE

Growth factors

(biotic potential)

Decrease factors

(environmental resistance)

Abiotic

Abiotic

Too much or too little light

Temperature too high or too low

Unfavorable chemical environment

(too much or too little of critical

nutrients)

Favorable light

Favorable temperature

Favorable chemical environment

(optimal level of critical nutrients)

Biotic

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

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

a population will increase if
A population will increase if….
  • A) Natality decreases
  • B) Mortality increases
  • C) Biotic potential increases
  • D) The environmental resistance increases
a population will increase if1
A population will increase if….
  • A) Natality decreases
  • B) Mortality increases
  • C) Biotic potential increases
  • D) The environmental resistance increases
slide12

Abiotic

Favorable light

Favorable temperature

Favorable chemical environment

(optimal level of critical nutrients)

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

exponential or logistic growth curve
Exponential or Logistic Growth Curve?

“Boom and Bust”

“Boom then stable”

logistic growth

Environmentalresistance

Carrying capacity (K)

Population size (N)

Biotic

potential

Exponential

growth

Time (t)

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
going up
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.
coming down
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.
population density
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

who s in control here
Who’s 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)
let s talk about sex old bio stuff
Let’s 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 don’t 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
what species are you

Carrying capacity

K species;

experience

K selection

Number of individuals

r species;

experience

r selection

Time

What species are you?
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)

Species

r-selected Species

K-selected Species

r selected species or k selected species6
R-selected Species or K-selected species?

HINT: The Capybara is the largest rodent in the world

survivorship curves

Late loss

100

Constant loss

10

Percentage surviving (log scale)

1

0

Early loss

Age

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)
isolation isn t best
Isolation isn’t 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.

oops i did it again
Oops! I did it again…
  • Past mistakes that need to be stopped:
    • Reducing biodiversity by destroying, fragmenting and degrading habitats
oops i did it again1
Oops! I did it again…
  • Past mistakes that need to be stopped:
    • Reducing biodiversity by simplifying natural ecosystems (monocultures – one type)
oops i did it again2
Oops! I did it again…
  • Past mistakes that need to be stopped:
    • Unintentional strengthening of pest species and anti-biotic resistant bacteria
oops i did it again3
Oops! I did it again…
  • Past mistakes that need to be stopped:
    • Elimination of natural predators (wolves, cougars, buffalo, eagles)
oops i did it again4
Oops! I did it again…
  • Past mistakes that need to be stopped:
    • Over-harvesting renewable resources
oops i did it again5
Oops! I did it again…
  • Past mistakes that need to be stopped:
    • Interfering with natural cycles in natural
oops i did it again6
Oops! I did it again…
  • Past mistakes that need to be stopped:
    • Over dependence on fossil fuels
4 guidelines for a sustainable future
4 Guidelines for a Sustainable Future
  • Our lives and economies are dependant on the earth and sun. They don’t depend on us.
  • Everything is interconnected.
  • You can’t 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.
slide48

Population

Control

Solar Energy

PRINCIPLES

OF

SUSTAINABILITY

Nutrient

Recycling

Biodiversity