Community Structure and Biodiversity

Predator Prey population cycle

Applying logistic growth to a consumer resource species interaction

Multiple interacting species rather than one singular species.

It has a cyclical pattern (going up and down over time)

Predator-prey population cycle

As the number of resources increases (carrying capacity), more resources for predators so predation increases.

food webs

Predator-prey cycles are embedded in ______ _______

food webs

______________ are not communities

Food web

• Model of consumer-resource interactions

• Includes predation, herbivory, parasitism

Food web

• Who eats who?

• Trophic interactions

• Does not include other species interactions

Community

• Group of interacting species

• Includes all species interactions, not just consumer-resource

Trophic pyramid

• only describes consumer-resource interactions 

• Size of level indicates energy contained in that level

• Helps you think about how food webs are structured

differences in energy between levels

Trophic pyramids indicate (by default) ….

cascades

• Effect cascades from one to the next to the next

• Direct and indirect effects

trophic cascade example

• There was kelp in marine system off the coast of california

• They were fed on by sea urchins

• The sea urchins are in turn eaten by sea otters (there were a lot of sea otters so there were a lot of otters that had a heavy effect on the urchins 

• This led to a heavy increase in kelp density as they were not being preyed on.

• Killer whales had eaten sea otters which lessened the sea otters population, increased the sea urchin population, thus killing off the kelp population. 

ecological cascade example

• Wolves have direct effect on coyotes and elk

• Since wolves chased the coyotes away, there are more pronghorn and small mammals around (indirect effect)

• Since wolves eat the elk, there is less resource for the bears so now they have to eat berries

• Since the scavenger birds like to hang in elk poop, the wolves have an indirect effect on them as the wolves eat the elk.

• Less elk will mean that there are more plants which can have an effect on beavers, stream locations, birds, and berry production

Top-down control trophic cascades

• Predators impacting lower trophic levels

• Species eating one another constantly happening

bottom-up control trophic cascades

Resource availability (space, nutrients, lights) impacting upper trophic levels

• Tension between them that is constantly occurring

• Top down is usually easier to observe

Both top-down and bottom-up occur simultaneously (trophic cascades)

trophic cascade example

• No big fish in system; means there will be a lot more smaller fish

• Not a lot of zooplankton because the smaller fish are consuming them

• Since there are no zooplankton, there will be a lot more algae because the plankton isn’t around to feed on it

• If there are bigger fish, there will be a lot more smaller fish

• Without smaller fish, there will be more zooplankton and ultimately less algae since the zooplankton are not being predated on and they are then consuming the algae.

more

Does more or less interactions yield a more stable community?

• The herbivore that was eaten by the predator is going to really increase in population size.

• Will exert a strong effect down into that system

• What happens when you remove the predator?

less

because there is still pressure

If you have a system with a lot of links, removing a species in the system will have______ of an effect on the other remaining species

More

If you have a system with less links, removing a species in the system will have _____ of an effect on the other remaining species

urbanization

• Massive alteration of an ecosystem

• Changes ecosystem processes

• Making it into what works for humans

• Changing how nutrients and water move through the system

• Changing soil and sediment composition

urbanization

• Alters species interactions

• Change in evolutionary/selective pressures

• Urban environment is becoming more important and more common for humans

Urban biodiversity

• Urbanization has a big effect on other species

• Forests and deserts are both better areas for species than an urban environment

• Biodiversity goes down in urban environments

ecosystem services

What is the importance of biodiversity?

ecosystem services

• Services that other species provide to humans

• Directly biological things, sometimes it's an ecological thing being altered by other species.

Non-humans

_______ are an important part of the ecosystems that humans rely on

Provisioning services

regulating services

cultural services

what are the three categories of ecosystem services?

Provisioning services

• Things that you can go out into the environment and pick-up, stock up and sell

• Ex: wood, food, medicines, cotton

regulating services

• These are things that we need that are not directly things that can be stocked up on

• Keeps our environmental systems working in a way that helps humans be successful

• Ex: water filtration, waste decomposition, crop pollination, climate regulation, disease control

Cultural services

• Experience this in different ways than compared to the other two services

• Ex: aesthetic, spiritual, personal growth, leisure and fun

biodiversity

Conserving _________ promotes human health

Wild/ Rural

• Non communicable disease reduction

• Competitive exclusion of pathogens

• Exposure to beneficial microbiota

• Habitat biodiversity

• Immune protection

• genetics/diet

• Immune protective habitat, rich in biodiversity and beneficial microbiota

Industrial/ Urban

• Low biodiversity urban habitat

• Not immune protective due to altered microbial exposure

Rewilded Urban

Urban habitat providing immune protective microbial exposure through biodiversity restoration

Food Webs

• A simple model of trophic interactions in a marine community

• Does not include non-trophic interactions

• Does not include indirect interactions

• Complexity creates disagreement on best way to quantify

• Not a great way to quantify biodiversity, but still important!

connectance

percent of possible vs. actual interactions

Species richness

(S) : the number of species in the samples

species evenness

ratio between estimated biodiversity and maximum

species dominance

inverse of species evenness

Functional ecology

Groups of similar species based on shared traits, similar niches/habitats, physiology, etc.

Keystone Species

• Species that have a disproportionate impact on the communities in which they live relative to their abundance

• discovered by Paine in 1966

Affects other species biodiversity and their relative abundance