Intro and Population Ecology Slides

Levels of organization we need to know:

• Biosphere: Life on earth

• Ecosystem: All biotic/abiotic factors in an area

• Community: all populations in an area

• Population: group of organisms, same species, in a specific area

Key to ecology = all living things are interdependent (themes of biology)

Types of ecology:

• Population ecology - study of how populations change

  • Populations are described by location, species, size, density, dispersion, and change

    • dispersion = how spread out a population is within a place

      • clumped (herds and groups), random, uniform (nesting site, defend your spot)

    • density = organisms per unit area

    • dynamics = how a population changes

      • how does it change: births/immigration (grow), deaths/emigration (shrink)

For factors lead to pop. change

B = # of birthds, D = # of death, I = # immgirants, E = # of emigrants, N = number of organisms, Delta N = Change in population

Delta N = (B - D)

Per capita birth rate = B/N

Per capita death rate = D/N

Exponential growth = No death occuring in a population (not really feasible long term), can occur in short periods of time

If B and D equal to eachother, that is the equilibrium point/carrying capacity (K)

• how many organisms a population can sustain based on conditions it has

Logistic growth = builds on exponential growth, includes the carrying capacity as an asymptote

• can change based on environment, does not have to be a perfect adherence to asymptote

Density-Dependent Factors:

• Competition for resources

• Stress

• Predation, parasitism, starvation, disease

Density Independent Factors:

• Amount of sunlight

• Temperature

• Atmosphere

• Water

Type 1 Survivorship: High survivorship young, as one ages, survivorship dips quick

Type 2 Survivorship: Survivorship stays same through whole life

Type 3 survivorship: Reproduce like crazy, lots of babies don’t make it, those that survive have high survivorship

Community Ecology

Humans are a walking community -- Species of bacteria interact in human bodies, fungi, parasites, etc

Species richness = number of species in a community

Biodiversity = number of a species in a community related to relative abundance of each species

• amount of each species x amount of species in community

• We like biodiversity (if destruction occurred, the biomass in a not biodiverse community is gone and the community is damaged)

The symbioses:

Ecological niche = Unique set of ecological requirements and roles for a species (temperature range, its diet, where it can live, etc)

• Sometime, niches overlap, causing organisms to fight over the same resources, creating competition

  • How can we deal with this competition?

    • Interference = Flock them off, interfere with their ability to get the resource

    • Exploitative = Take it all!

  • Can cause competitive exclusion = when one species is driven to extinction/near extinction due to competition over a resource

    • can result in niche partitioning - instead of competing, organism will take a smaller part of their niche to avoid other organisms

Mutualism = opposite of competition, a cooperative relationship in which both species receive a benefit

• EX: pollinators and flowers; the pollinator gets nectar, the flower gets its genes spread

Commensalism = One species benefits from a relationship, the other is “unaffected”

• EX: Water buffalo, cape buffalo, birds; birds sit on top of water buffalos to scare insects and then eat them (no cost to the buffalo)

• Lots of commensalism groups might only be there because we don’t fully understand them

How do communities change?

• Succession - sequential, gradual growth/regrowth of a species in an area

  • usually plants

  • Primary succession:

    • Pioneer species = first species that grow that lead to the intermediate species

      • quick, small, quick reproducing, kickstarts the progress\

      • changes the environment to start succession

    • Intermediate species = growing version of the primary species

    • Climax community = full grown species in community

      • no change after

      • stable end point until disturbance “resets” the process

    • Takes thousands of years

  • Secondary succession:

    • Primary succession happens in a place that already had a climax community but was wiped out

    • Happens in less time than primary succession since there is already soil/seed built up

Intermediate disturbance hypothesis: Diversity and species richness is highest with a moderate level of disturbance

• If disturbance is too low, too much climax community, too little diversity

• If disturbance is too high, climax communities will never develop, only pioneer species

• If disturbance is just right, you will have both climax, intermediate, and pioneer species

Available size in a habitat and distance from a colonizing source (mainland) impacts biodiversity

• The farther away a community is from the mainland means less likely for more species to come, more diversity

• Larger islands have more space for more species, more opportunities/resources than small islands, lower mortality rate

Indicator species (aka bioindicator) = Species that tell us a community is healthy

• Lichen -- if air is good, white lichen will live/grow, if air is bad, lichen will die

Keystone species = A species that is vital to functionality of an ecosystem, remove of this species may lead to a collapse

• Sharks -- top down control, keep things stable from their presence (will eat rays, rays eat arthropods)

  • No sharks? The rays eat all arthropods, not enough arthropods, the rays die.

Endemic species = Species that are native to one specific location and ONLY that

• Birds of paradise (only live on new guinea)

Exotic species = Species that live in places they are not native to, evolved elsewhere and established in a different place

• Many are invasive, ie spotted lantern fly

Ecosystem Ecology

Focuses on how living and nonliving things interact

• how living things change nonliving things

Energy will flow in an ecosystem and nutrients will be cycled

• Autotrophs can capture available energy and turn it into usable cell thingies

• 90% of energy is lost at every trophic level

  • b/c of metabolism, inedible parts,

• Food webs illustrate the transfer of energy/nutrients between producers and consumers

  • cho cho chon chonp nutrients get cycled

Carbon Cycle

• water acts as a carbon “pool”

Water Cycle

Nitrogen Cycle

• Bacteria/fungi can turn nitrogen into usable nitrogen

Phosphorus Cycle

• Terrestrial cycle -- no atmospheric phosphorus

• Phosphorus locked in rocks/soil get consumed by other stuff

  • It is rare, it’s a limiting factor (populations don’t grow bc of limited phosphorus)