Lecture 13a:Ecology

Lecture 13a:Ecology

EcologyDefinition: the study of interactions between all of the living and non-living components in an environment

So, discussion of ecology can include

Animals and plants

Soil and water qualities

Climate

Human impacts

Communities

Definition: assemblage of populations of multiple species within a single environment

Ex: Fallen log

Ex: Forest

Fairly broad- can be small or large

Communities

Because the organisms in a community have lived together over a long period of time, opportunity for coevolution

When an evolutionary change in one organism influences an evolutionary change in another organism

Ex: Many flowers and their pollinators

Coevolution

Interactions

Communities do not exist in a vacuum- the organisms interact with each other and with the environment-- this is an ecosystem

Community CompositionSpecies richness: what species make up a community- basically just a list

Diversity: richness plus species distribution and relative abundance within the ecosystem

If different species spread throughout, more diverse than if only one is abundant

Succession

Communities change over time- but can take decades to see the changes

Succession is the process of an ecosystem moving to a climax community after a disturbance

Each particular environment will lead to a stable climax community-a specific assemblage of plants and animals best suited to that environment

Primary Succession

Occurs when ‘new’ land becomes available- starts from bare rock or sand after glacier

retreats, lava flows, etc.

Secondary Succession

Occurs after a disturbance- fire, agriculture, etc- there is already soil

present

Succession

In either case, first species are pioneer species- small, short-lived, and quick to mature (i.e. weeds)

First in primary are lichens and mosses- lichens help break down rocks into soil

Gradually, more equilibrium species move in- both plants and animals

Ecological Niche

Niche: the specific ‘role’ of the organism in the ecosystem, including what it eats, where it lives, when it is active, how it interacts with others

Habitat: the part of the ecosystem that the organism in question lives in

Ex: Ecosystem for hippos is African savanna, habitat is the river and surrounding shorelines

Interactions

Organisms interact with each other constantly, both within and outside of their species

Interactions, called symbiotic relationships, can be either positive or negative for each

CompetitionCompetition can be for food, space, nutrients

Competitive exclusion principle: no two species can occupy the same niche at the same time

Leads to niche specialization, a way to reduce competition where different species use different resources, even though both could potentially use the same one

Competition

Character displacement- organisms that have partitioned resources will evolve to suit their acquired niche, and thus the characteristics in question will become more different over time

Ex: bird beaks in birds that eat different foods

Character displacement

Spoonbill-uses bill like a shovel in sand

Pelican- catches fish under water

Heron- stabs larger fish

Skimmer- uses bottom bill to scoop fish from surface

MutualismA relationship in which both members benefit

Also very important

Ex. plants and pollinators

Ex. lichens (algae and fungus, living together)

Ex. Ants and caterpillars

http://www.youtube.com/watch?v=z3bWqlPLpMg&feature=BF&list=PLD91727B50EF35272&index=2

Predation

When one animal eats another

Parasitism is a form of predation in which the predator lives in or on the prey, called the host

Ex: cheetahs and gazelles

Ex: owls and moles

Ex: hookworm and humans!

Commensalism

Relationship when one organism benefits and the other is neutral

Ex: One animal transports another

Ex: Sea anemones and clown fish

Fish: gets protection from

predatorsAnemone: doesn’t

care

Name That Relationship!

Microhylid frog + tarantula?

Name That Relationship!

Hermit crab + sea anemone

Name That Relationship!

Ants + acacia trees

Name That Relationship!

Cerambycid beetle + pseudoscorpion

Community StabilityReally, communities are fragile, not stable- stability is hard to achieve because of natural disasters, human encroachment, etc.

Keystone species are species that help to stabilize community, other species’ survival can depend on this one species

Frequently not abundant

Ex: grizzly bears

Ex: bats in tropical forests

Keystone Species: Sea OtterSea otters live in kelp forests

Eat lots of sea urchins, keep populations low so urchins don’t eat all the kelp

However, fishermen want to remove otters because they also eat abalone

But, if all otters are gone kelp forest will be gone and abalone will be gone because urchins will eat all the kelp and destroy the ecosystem

Role of OrganismsHow an organism feeds is part of its niche:

Autotrophs: take in inorganic nutrients (CO2, minerals) and outside energy source

Plants, algae

These organisms are producers, because they produce food

Role of OrganismsHeterotrophs: need a source of organic nutrients, release CO2

Called consumers, because they consume food

Four types:

Herbivores: eat plants

Carnivores: eat other animals

Omnivores: eat both plants and animals

Detritivores: decompose wastes and dead material

Energy and Chemical Flow

Solar energy enters ecosystem through plants

Plants convert this into chemical energy via photosynthesis

Chemical energy is used by animals

At each level, some energy is used, some lost as heat

Less energy is available to the next level

Chemical Cycles

Plants use nutrients in the soil to make organic compounds

Animals eat the plants and use those compounds

When animals die or eliminate waste, nutrients are broken down by detritivores and returned to soil, available to plants again

Food Webs and Energy/ Chemical FlowFood webs represent energy flow from Producers to Primary Consumers to Secondary and Tertiary Consumers

Can also be drawn to represent detrital food webs, showing what eats waste

Important to realize where energy is stored- may be in living matter (rainforests) or in dead materials (temperate forests)

Trophic Levels

There are always fewer consumers than there are producers, because energy is always lost as heat and used for cellular respiration and growth in every organism

As a general rule, only 10% of energy in one level is available to the next

Another way to see it

Biomass: it takes 10,000 g of grass to support 10g of snake

Primary ProductivityRate at which producers capture and store energy

Depends on species, temperature, moisture, soil

Highest in tropical environments, lowest at high altitudes, tundra, desert

Think of how this relates to high species richness and diversity in tropical rainforest vs. tundra

Rainforest

Tundra