bio exam 3

Food webs

illustrates how energy moves within communities bc it illustrates who eats who

Trophic levels

levels in a food chain/webs

comprised of producers, primary secondary, tertiary, and quaternary consumers

fewer organisms in the upper levels

first trophic level

photosynthetic organisms

second trophic level

decomposers, mutualists, pathogens, parasites

third trophic level

predators, grazers

4th, 5th, etc trophic level

higher level predators

rule of tens

only about 10% of the energy at 1 trophic level is transferred to the next

roughly 90% lost

species that are in the same trophic level AND consume the same organisms are

grouped into GUILDs

energy movement limits

species abundances

as energy moves to higher trophic levels,

can support fewer organisms

strong interactions

involve a few species that have major influence on community structure

Foundational species

have substantial influence on the community based on their biomass

arrows in a food web represent

flow of energy within an organism
represents how only a small amount of energy moves within food webs

keystone species

maintain community stability by maintaing species diversity

act as predators to keep pop in check

apex predator

top animal at the highest level of the food chain

what is the apex predator, foundational species, and keystop species

apex: orca
keystone species: otter
foundational species: kelp

what is the top down effect is this interaction

• Orcas increase predation on sea otters, causing sea otter abundance to decrease.

• With fewer sea otters eating them, sea urchin biomass increases.

• More sea urchins graze on kelp, so kelp density decreases

what is the bottom up effect in this interaction

• Kelp provides food for sea urchins.

• More kelp can support more sea urchins.

• More sea urchins provide more food for sea otters.

• Greater sea otter availability can influence the food resources available to orcas.

guilds

species in the same trophic levels that consume organisms

bottom up

producer influences upper trophic levels

top down effects

when predators in higher trophic levels have increased, indirect effects on lower trophic levels

Ecosystem engineers

special type of keystone species

drastically shape the habitat for their own fitness

results in shifts that infleunce other species in an area

keystone v. dominant species

biomass is higher in the domant species

biomass

the total mass of living or recently living biological organisms—including plants, animals, and microorganisms—within a given area

Alternative Stable states

when a community is disturbed so much that the species composition and relative abundance of populations in the community change, and the new community structure is resistant to further change

community resistance

the amount that a community changes when acted upon by the same disturbance, such as the + or - of a species

succession

the process by which the species composition of a community changes over time

seral stage

each stage of community change during to process of succession

pioneer species

the first species that are observed after a disturbance

climax community

the final stage in the process of succession

conducted a seed transplant experiment in the sand dunes near Lake Michigan and monitored seedling survival in the next

found that grew best where they are typically found

Number of seeds

Early succession: Many
Late Succession: Few

Seed size

Early succession: small
Late Succession: large

Mode of dispersal

Early succession: Wind or stuck to animals
Late Succession: gravity or eaten by animals

seed viability

Early succession: long
Late Succession:short

root:shoot ratio

Early succession: low
Late Succession: high

growth rate

Early succession: fast
Late Succession: slow

size at maturity

Early succession: small
Late Succession: large

shade tolerance

Early succession: low
Late Succession: high

primary succession

involves no living material, no plant life

bare

secondary succession

occurs after a disturbance with living organisms

mechanisms of succession

facilitation
inhibition

tolerance

facilitation

where the presence of one species increases the probability that a second species can become established

inhibition

when one species decreases the probability that a second species will become establsihed

tolerance

probability that a species can become established depends on its dispersal ability and its ability to persist under the physical conditions of the environment

all mechanisms of succession afffect which

orgnaisms can become established at later points in time

chronosequence

a sequence of communities that exist over time at a given location

assumptions are all environments have facilitation, inhibition, and tolerance

investigated directly and indirectly

What are the stages of whale fall succession

1. mobile scavenger phase

2. enrichment-opportunist stage

3. self-fulfilling stage

4. reef stage

mobile scavenger stage

initial scavengers (higfish, sharks, marine isopods, etc) eat flesh

enrichment-opportunist stage

smallar organisms comb surrounding area for other organic matter

self-fulfilling stage

bacteria and other oranisms break down bone, releasing hydrogen sulfide that toher microbes can use

reef stage

remaining bone could provide structual support for remaing suspension feeders

priority effect

when the arrival of one species at a site offer to the subsequent colonications of other species

in floral microbe communities,

colonizaiton by previous microbes results in significant changes in pH that influences consequent colonization

how can bird perches help restore disturbed areas

They attract birds that may deposit seeds, helping plants colonize the area.

How does seed dispersal contribute to succession?

It allows plant species to reach disturbed areas and become established.

facilitation ex

On sand dunes, pioneer plants stabilize the sand and add organic matter, making it easier for other plants to grow.

inhibition ex

A plant grows densely and blocks sunlight, preventing other plant species from growing underneath it.

tolerance ex

A shade-tolerant tree seedling grows beneath an established forest canopy because it can survive with limited sunlight.

ecosystem

oe or more communities of living organisms interacting with their nonliving physical and chemical environment

focus on cycling of energy and matter

law of conservation of matter

matter cannot be created or destroyed; it can only change form

law of conversation of energy

energy cannot be created or destroyed; it can only change form.

This is also known as the first law of thermodynamics.

Matter

the material substance that constitutes the observable universe

form the basis of subjective phenomena

biomass from product

energy

capacity for doing work

potential, kinetic, thermal, electrical, chemical, nuclear

photoautotrophy v. chemoautotrophy

both use external sources of energy (light or chemical reactions) to power carbon fixation (incorporating C from CO2 into organic matter)

Primary productivity

the production of new organic matter of biomass within an ecosystem

Photoautotrophy ex

CO₂ + H₂O + light → CH₂O + O₂

Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to produce glucose (sugar) for energy and growth. This process occurs in the chloroplasts, where chlorophyll absorbs light energy, and oxygen is released as a byproduct.

chemoautosynthesis ex

sulfide oxidation
CO₂ + 4H₂S + O₂ → CH₂O + 4S + 3 H₂O

•Energy from sulfide oxidation (instead of light) powers carbon fixation

•Note parallels with photosynthesis

some deep sea foodwebs are

dependent on bacterial chemosynthesis for energy

gross primary productivity (GPP)

the rate at which energy is captured and assimilated by produces in a given area

net primary producitivity (NPP)

the rate energy is assimilated by producers and converted into producer biomass in an area

NPP=

GPP - maintenance (energy required to keep the plant alive)

standing crop

the biomass of producers present in a given area of an ecosystem at a particular moment in time

how do we measure primary productivity

change in biomass of producers over time

movement of Co2/O2 over time

change in CO2 and O2 reflects

productivity

why would adding nutrients increase primary production

influences primary producers