Biology topic 16: Communities and Ecosystems

Community

All the organisms living in a certain area

Coevolution

When 2 species evolve together and help shape each other

For coevolution to happen…

• 2 species have evolved in the same place for millions of years

• each has been a force of natural selection on the other

Outcome of coevolution:

evolutionary adaptations develop in one or both species in response to the other

Interspecific interactions

when members of different species interact, can have positive / negative impacts on species

Symbiosis

living together in a prolonged relationship (not necessarily a good thing!)

Competition

harms both species involved.

Interspecific competition is most intense when ecological niches overlap and a resource is scarce.

ecological niche

role of a species in its community

– Its food

– Where it lives

– Resources it needs

Predation

when one animal (the predator) eats another (the prey)

Herbivory

animals eating plants (herbs)

Predation and herbivory lead to diverse___________

adaptations (in both the eater and the eaten)

Protective Adaptations in Prey:

• Camouflage

• Mechanical and chemical defenses

• Warning coloration: bright coloration to advertise

distastefulness or toxicity

• Mimicry – resembling another organism

• Startle coloration- color/pattern is flashed, surprising predator so prey can escape

Adaptations Shaped by Herbivory:

Leads to diverse plant adaptations

– Toxicity

– Spines and thorns

– Even false eggs on leaves

• Herbivores can develop immunity

to toxins and other ways to still eat

the plants

Commensalism

one species benefits and the other is not helped or harmed

Mutualism

both species benefit!

examples:

• Pollinators and flowers

• Corals and zooxanthellae

Parasites and Pathogens

live on or in a host from which they obtain nutrients

• They benefit but the host is harmed

Pathogens

cause disease in the host.

Some parasites are pathogens, others

cause malnutrition or just discomfort.

Parasites

can be internal (tapeworm) or external parasites (mosquitoes, aphids)

Two components of Species Diversity:

• # of different species (species richness)

• How many of each species (relative abundance)

Foundation Species

Help form and shape the community

–Often producers and very abundant

–Often change the physical environment where they are found

Examples of foundation species

• giant kelp

• Coral in coral reefs

Keystone Species

Help maintain a community

•Their removal causes other species to disappear

Sea Stars (Pisaster) is a:

Keystone Species.

-Eats mussels and keeps them in check

–Keep mussel population low and other species can survive

Invasive Species

Species are brought by humans into an ecosystem in which they did not evolve

–Sometime intentional, sometimes accidental

•Many don’t survive

•Ones that do are called ‘exotic’ or ‘non-native’

Introduced species that spread and proliferate are called:

INVASIVE species

Some examples of invasive species: (Found on page 5 of the study guide)

• Chytrid fungus

• Zebra mussels

• Asian carp

• Tumble weed

Ecosystem

All the organisms in a given area along with their nonliving environment

Biotic parts of an ecosystem

all living things

Abiotic

All nonliving things

Tropic structure is…

Feeding relationships

Energy flow

the passage of energy through the ecosystem

At each level, most energy is lost

–Only __% of energy gets to the next leveL

10% of energy gets to the next level

–This is the 10% rule

Producers

bottom level gets energy from the sun

Consumers

All higher levels get energy from eating other organisms

Scavengers

• Eat fresh dead stuff

• Crows and vultures brittle stars and shrimp, maggots

Detritivores

• Eat decaying material

-earthworms, millipedes, sea cucumbers

Decomposers

• Secrete digestive enzymes to break down food outside their body

• Mainly prokaryotes and fungi

Humans can be…

Primary consumers OR secondary consumers

Info on the flow of energy and the cycle

Energy continuously flows through ecosystems

–Energy enters as sunlight, flows through the food chain, then leaves

•The matter is recycled in ecosystems

–Life takes chemicals from the environment (nutrients)

–Through decay, those elements are released back to the environment

–The cycle starts again

–Chemicals do not enter or leave

What is a biogeochemical cycle?

The cycling of matter into life and then back to the environment

Important cycles in the biogeochemical cycles are…

• carbon cycle

• Nitrogen cycle

• Water cycle