Ecology: Everything Else 

Communities (From 4/23) A group of interacting populations that occupy the same area at the same time. Living things only Organisms adapt to the conditions under which they live. What factors might influence tropical fish community?

Limiting Factors and Tolerance A limiting factor restricts the…of organisms Number Reproduction Distribution Could be biotic (e.g. competition for food) or abiotic (e.g. temperature) Range of tolerance – upper and lower limit of a particular limiting factor Example: steelhead trout live in a temperature range of 9-25 °C Conditions under which they can live (might not necessary thrive)

Ecological Succession How might an ecosystem respond to a drastic change in biotic/abiotic factors? Example: forest fire

Primary Succession The establishment of a community in an area of exposed rock that does not have any topsoil Example: Solidified lava flow First step: Lichens (a mutualistic relationship between a fungus and an algae) and mosses As they die, they make first layer of soil Example of a Pioneer species Later: weedy plants (grasses and ferns) Much later: shrubs and trees

Secondary Succession A process that occurs after a disturbance has taken place, but the soil remains Example: forest fires What’s different about the time scale? Thought question: notice the species at the start and at the finish

When does succession “end?” Unclear. (hard to tell) Climax community – when a stable community has formed What role might humans play?

Population Ecology Chapter 5 https://www.ined.fr/en/everything_about_population/videos/the-world-population-full-version/

Species Occur in Groups Called Populations Population density – the number of organisms per unit area Species distribution (dispersion patterns) Based on the availability of resources (food) Examples in the notes section of PowerPoint Pattern of spacing within an area (based on the organism’s needs). Examples Clumped – American bison Uniform – black bears Random – White-tailed deer

Population-limiting Factors Both of these types control population numbers, but in different ways Density-independent factors – do not depend on the number of organisms per unit area Abiotic factors – weather events like drought, flooding, extreme temperature, or tornadoes Forest fires – crown v. controlled fires

Density-dependent factors Any factor that depends on the number of members per unit area Usually biotic factors Disease – outbreaks occur when population density is high Parasites – can limit the population size when population density is high Competition – increases when population density is high

Lemmings – Competition Population grows exponentially until food become limited and the population sizes decreases significantly

Population Growth Population growth rate explains how fast a population grows Birth rate Death rate Emigration – moving away from a population Immigration – moving into a population

Exponential Growth – J-Shaped No limits placed on a population by its environment Numbers Time

Logistic Growth – S-shaped Most populations Growth slows when the carrying capacity is approached The maximum number of individuals that an environment can support in the long-term Determined by energy, water, oxygen, and nutrients available

Reproductive Patterns r-strategy – resources fluctuate Carrying capacity varies Produce as many organisms as possible to take advantage when resources are high Insects k-strategy – resources are constant Carrying capacity is constant Produce only a few offspring that have a better chance of surviving Large mammals

Human Populations Click the link below for a quick video on human population! https://www.youtube.com/watch?v=sc4HxPxNrZ0

Demography Study of human population size, density, distribution, movement, and birth/death rates Why is the human population increasing more rapidly now than it did in the past? Technological advances Modern medicine

Age Structure in Human Populations Number of individuals in age groups No or negative growth. Think about why these different countries would have different kinds of growth!

Human Carrying Capacity Can we increase our carrying capacity forever? How much time do we have? Population ecologists predict a global population of 8.110.6 billion people in 2050 Estimate – 10-15 billion How can we manage the use of our resources? Sustainability! (look it up)

Biodiversity and Conservation Chapter 5

Biodiversity Variety of life as determined by the number of different species in a given area Three types Genetic diversity – variety of genes or inheritable characteristics Species diversity – number and abundance of different species in a community Ecosystem diversity – variety of ecosystems in the biosphere

Genetic diversity in a vole population Species diversity in a coastal redwood ecosystem Community and ecosystem diversity across the landscape of an entire region

Why is Biodiversity Important? Direct economic value – food, energy, clothing, energy, medicine, and shelter. Indirect economic value – green plants provide oxygen, cycles provide clean drinking water (New York City, 1990) Aesthetic and scientific value 6 billlion on water filtration, or 1.5 billion on cleaning up watersheds!