Chapter 4 – Population Dynamics

  1. Population – Interacting group of individuals of a species that use common resources and are regulated by the same natural phenomenon.
  1. Population Density – Number of individuals of a species/unit area or volume
  2. Mark – Recapture Method –
  3. Traps are set out
  4. Animals are tagged (marked) and released
  5. After time, traps are reset.
  6. Marked and unmarked organisms are recaptured
  7. N (# of individuals in population) = marked individuals x total caught second time

Recaptured marked individuals

This creates an estimate of the population

  1. Spatial Dispersion Pattern – way individuals of a population are spaced within their area. – pg. 94
  2. Clumped – aggregate in patches; most common in nature – results from unequal distribution of resources
  3. Uniform – even patterns resulting from interactions among individuals – often results from competition for space and nutrients
  4. Random – are spaced in a patternless, unpredictable way. This is rare – occurs when multiple resources are affecting them in conflicting ways - a mixture of factors such as oxygen, food, shelter, predators, etc.
  1. Population Ranges – area in which population is found. The borders of a population.
  1. Limiting Factors – factors which control a population size
  1. Density Dependent Factors – factors controlling population size that depend upon the density of the

population – has the greatest effect as the number of population increases

  1. Competition – for food, water, space, sunlight

Number of individuals ----- increases competition for basics

2. Predation – prey population is large ------increases predator population ----- decrease prey

population ---- decreases predator population and it continues. This controls natural populations

3. Parasitism – feeds on another organism and harms it.

-best in dense populations – easier to spread to other hosts

-best if not too deadly so parasite can reproduce and doesn’t kill the host

4. Build-up of waste material becomes toxic

5. Crowding and stress – population number is lowered due to higher deathrate and lower

reproductive rate. Contributing causes are

Increased crowding + increased competition for food and fighting

Increased stress of above = decreased immune system, hormonal

imbalance and eating of offspring

B. Density Independent Factors – abiotic factors that do not have to do with how dense a population is –

examples = frost, tornadoes, flood, natural occurrences that wipe out a population, then it regrows

  1. Exponential Growth – whole population multiplies by a constant factor during constant time intervals. It is an idealized picture of unregulated growth in a population. Pg. 702 – This happens if not limited by some factor – population grows faster and faster 1,2,4,6,8,12, etc. each twice the preceding number. Bacteria does this.
  1. Population Limiting Factors – environmental factors that restrict population growth – see pg. 704 Logistic Growth Model/Curve

a = begins to growb = exponential growth – birthrate deathratec and d = Birthrate decreases or deathrate increases

e = steady rate = growth rate = zero (really varies up and down around this point)

f = carrying capacity = how big a population can be supported by the environment without a net increase or decrease

  1. Boom-bust Cycles – When Predator/Prey populations seem to cycle with rapid increase and decrease over set periods of time
  1. Life/Survivorship Curves – predict the probability an individual will survive –
  1. Type I curve –

Few offspring but give good care – whales, elephants, humans

  1. Type III curve –

High death rate in young then death rate slows for survivors – oysters, insects

  1. Type II curve –

Intermediate – fairly constant mortality rate over time – invertebrates, some mammals

  1. Boom-bust Cycles – When Predator/Prey populations seem to cycle with rapid increase and decrease over set periods of time
  1. Human Population Growth – decreasing in industrialized countries, increasing in developing countries
  2. Zero Population Growth – ZPG = birth rate equals death rate
  3. Age Structures – Graphs that show the number of males and females in five year increments for three areas – pre-reproductive , reproductive and post-reproductive periods.
  4. Human Carrying Capacity – individuals in industrialized countries are using more natural resources than those in developing countries. If world population reaches above carrying capacity of biosphere death and starvation will occur.

Ch. 5 Notes – Biodiversity and Conservation

  1. Biodiversity - variety of life in an area determined by the number of different species in that area. Increases ecosystem stability.
  1. Genetic Diversity – variety of genes or inheritable characteristics in a population
  2. Species Diversity – species richness and species abundance. Species diversity is highest at the equator
  3. Ecosystem Diversity – variety of ecosystems present in biosphere.
  1. Biodiversity Impt. – economic, aesthetic and scientific reasons
  1. Economic Value – provide food, clothing, energy, medicine, shelter, oxygen, water
  2. Aesthetic and Scientific Value – Emotional value (imagine a barren world – YUK!!!!), most medicines were manufacture were originally from plants (esp. in rain forest)
  1. Biodiversity Threats –
  1. Extinction Rates – Background extinction is the normal process of a species becoming extinct over time as their environment changes. Mass extinction is when most living organisms become extinct in a short period of time. Comparing today’s rate of extinction to that of the fossil record leads scientists to believe we are in a period of mass extinction (ext. rate about 1000 times the background rate)
  2. Overexploitation – overuse of a species for economic reasons until the species ceases to exist
  3. Habitat Loss – number one cause of extinction today
  4. Clearing/destruction of a habitat
  5. Disruption of habitat – events cause a sequence of changes resulting in the extinction of one or more species
  6. Fragmentation of habitat – separation of an ecosystem by human made barriers i.e. interstates, dams, man-made lakes
  1. Pollution –
  2. Biological Magnification – increasing concentration of substances in organisms as trophic levels increase in a food chain or web. Ex – DDT
  3. Acid Precipitation – burning of fossil fuels releases sulfur dioxide and nitrogen dioxide into air. They react with water (rain) to form sulfuric acid and nitric acid. This rain reduces nutrients in the soil and lakes and changes their pH.
  4. Eutrophication – substances rich in nitrogen and phosphorous (fertilizers, animal waste, sewage) flow into freshwater aquatic environments causing an overgrowth of algae. Algae uses up all of the oxygen so fish and other organisms suffocate in water.
  5. Introduced Species – species that are not indigenous (naturally occurring in the area) upset the ecosystem balance. They often become invasive and overgrow due to lack of predators in the area.
  1. Conserving Biodiversity –
  1. Decrease use of natural resources
  1. Renewable Resources – resources replaced by nature faster than they are consumed. If demand exceeds supply they become depleted
  2. Non-renewable Resources – are found in limited amounts or take long time periods to replace. Ex: fossil fuels, mineral deposits
  3. Sustainable Use – using resources at a rate at which they can be replaced – RECYCLING !!!!!!!!!!!
  1. Protected areas – areas that have been established by the government (local, national or international) that slows use of resources to a sustainable level
  2. Monitoring Biodiversity Hot Spots – 34 world-wide (pg. 132) – to qualifyregion must meet two criteria
  1. Must be at least 1500 species of endemic (occur only there) vascular plants
  2. Region must have lost at least 70% of its original habitat
  1. Biological Corridors – connect fragmented habitats so organisms may move and genetic variation increases
  2. Bioremediation – use of biological organisms to clean or detoxify polluted areas – often bacteria, fungi and some plants
  3. Biological augmentation – adding natural predators to a degraded ecosystem to improve ecosystem
  4. Legal Action – passage of local, national and international laws to protect organisms.