Presentation on theme: "Population Ecology (chapter 14 -- sect 3 and 4) Intro to Chapter 16 – Human pops Each population has A Density A Dispersion A Reproductive Strategy."— Presentation transcript:
Population Ecology (chapter sect 3 and 4) Intro to Chapter 16 – Human pops Each population has A Density A Dispersion A Reproductive Strategy
Population A group of the same species of organism living in the same place Understand food chains and food webs What might effect the survival of THIS group of dolphins?
Characteristics of Populations 4 Major Characteristics of Populations: –Geographic Distribution –Density –Growth Rate –Age Structure
–Area inhabited by a population *remember, there are also ecological equivalents in similar ecosystems around the planet, but if they are not in the same habitat, they are NOT the same population! 1. Geographic Distribution
Population dispersion Way in which individuals of a population are spread in an area or a volume 3 types: Dispersion patternsDispersion patterns -- page 437 in textbook Clumped Uniform Random
# of individuals in population per unit area –(# individuals) / (area) –Varies depending on species in ecosystem –Increase density = increase crowdedness 2. Population Density
Example: 150 bullfrogs live in a pond that covers an area of 3 square kilometers. What is the bullfrog’s population density?
Answer: 50 bullfrogs per square kilometer
How fast a population is growing/shrinking 3. Growth Rate
Negative & Positive Growth Positive growth: net increase –Total penguin population was 1200 at the beginning of the year, now is Negative growth: net decrease –250 penguin chicks died during the year.
Biotic Potential The maximum rate at which the population of a given species can increase when there are no limits on its growth. The maximum rate at which the population of a given species can increase when there are no limits on its growth. “living” potential It is not possible for a population to increase FOREVER – there are limitations!
1.Immigration: movement into an area 2.Emigration: movement out of an area ***approach maturity & move out ***shortage of resources 3.Birth Rate Change in # births 4.Death Rate 1.Change in # deaths ***increase/decrease birth & death rates ***birth = death? Factors affecting population growth
Types of Population Growth Exponential Growth Logistic Growth
J-shaped curve reproduce at a constant rate –Slowly at first, then larger until approaches infinitely large size. ideal conditions unlimited resources 1. Exponential Growth
S-shaped curve –Slow increase, larger increase when large number of resources, then slows when resources become less available, growth slows/stops, oscillates around carrying capacity. Carrying Capacity- –largest # individuals environment can support –Tells size of population when average growth rate reaches zero. How could growth slow or stop? 2. Logistic Growth
How population growth may slow: –Birth rate decreases –Death Rate Increases –Both occur at the same rate Reason why these change Limiting factors
causes population growth to decrease Limiting Factors
1. Density Independent Factors Do not depend on population size Ex: Unusual weather natural disasters seasonal cycles damming rivers clear-cutting forests
2. Density-Dependent Factors depends on population size. Competition Predation Parasites Diseases Competition Predation Parasites Diseases larger populations are more affected by density-dependent factors (orgs are closer together)
Q1: Think about the black racer snake populations in Georgia. Once a pair of mice start reproducing, what would happen to the black racer snake populations, and why? Application
Answer They will increase because there will be more mice to feed them. Q2: If the mice population dies off, what would happen to the snake populations, and why?
Answer: The snake populations would decrease, because there would be fewer mice to eat. GRAPH this senario! What is the GENERAL shape and height of each curve shown…
Below is called a TRACKING GRAPH – because the peaks of the predators always follow the peaks of the prey
2a. Competition compete for resources when population becomes overcrowded. I only have 5 bottles left
Types of Competition InterspecificIntraspecific
Interspecific Competition Competition between different species for the same resources. wildebeast and rhinovultures and hyenas
Intraspecific Competition Competition between members of same species for similar resources. lions Bunchgrass in Mojave Desert – roots compete herons
1b. Parasitism and Disease Parasite or disease-causing organism takes nourishment from host, weakens/kills host spreads quicker w/ greater density. Wasp Cocoons This larval sphinx moth has been attacked by a parasitic wasp. The wasp inserted its eggs beneath the moth’s skin. After hatching, the wasp larvae fed on their host internally until they appeared as white cocoons on its back.
Demography Study of human population growth characteristics Looks at growth rate, age structure, geographic distribution Can tell if pop is growing by looking at the difference between the birth rate and the death rate In US, death rate is declining, life expectancy is increasing, fertility rate is decreasing – WHY?
Age-Structure diagrams or Population Pyramids Describes how many individuals of different ages make up a population Population Pyramids, or Age-Structure Diagrams, show age structure in a population. Populations with large numbers of young offspring have greater potential for rapid growth
Comparing Human Populations… Expansive ConstrictiveNear Stationary
Patterns of Population Growth… The Demographic transition- A change in a population from high birth and death rates to low birth and death rates.
Human Population on Earth Thomas Malthus – economist, late 1700’s *wrote an essay that stated that human population was growing faster than the Earth’s resource could support Today’s human population exceeds 6 billion…
Human Population -- predictions
Carrying capacity and humans Carrying capacity for human pop has changed due to technology Due to improvements in: Agriculture, transportation, medicine, sanitation
Nonrenewable vs. renewable resources Nonrewable – used faster than they form ex. Coal and oil Renewable – cannot be used up or can replentish themselves over time ex. Wind energy If not used carefully, renewable COULD become nonrenewable Ex. Water – pollution often makes it unusable
U.S. uses more resources and produces more waste…. Than any other country on the planet ex. 230 million tons of garbage/year (4.2 lbs per person per day) Ecological footprint: The amount of land necessary to produce and maintain enough food and water, shelter, energy, and waste Depends on: amount and efficiency of resource use, and the amount and toxicity of waste produced See textbook page 487 for world view