Ecology 1: Ecosystems

Levels of Organization• Organism

• Ex. an elephant

• Population– A group of individuals in the same species, living and

interacting in one area• Ex. a herd of elephants in the Serengeti

• Community– Multiple populations interacting in one area

• Ex. grazing antelope, elephants and giraffes in the Serengeti

• Ecosystem– All populations in one area interacting with each other and

their non-living environment.• Ex. the Serengeti (all organisms plus climate, nutrients, etc.)

Levels of Organization• Biosphere

– All areas of the earth from the ocean depths to the atmosphere that support life.

Ecological roles

• Autotrophs - Producer • makes own food (through photosynthesis or

chemosynthesis)

• Heterotrophs - Consumer • must eat other organisms for food; • primary (mouse), secondary (fox), tertiary (bobcat)

– Herbivore (eats plants) Carnivore (eats meat) Omnivore (eats both)

– Detritivore• Organisms that feed on animals remains and dead material

(crabs, earthworms)

– Decomposer• An organism (ex. fungi or bacteria) that completes the

final breakdown of materials in an ecosystem• End of 3.1

How does energy enter the ecosystem?

– Energy hits the earth in the form of sunlight

– Autotrophs convert sunlight (or chemical) energy into organic molecules

– Less than 1% of the sun’s energy is converted into organic material

– Eventually all energy is lost back to the atmosphere as heat.

How does energy move through an ecosystem?

• Energy trapped in autotrophs (producers) then gets transferred to heterotrophs (consumers) as one organism eats another

• The easiest way to show this is by using a food chain, food web, or food pyramid.

• Food chain – series of steps in which organisms transfer energy by eating and being eaten.

Food Weblinks all ecosystems in a food chain together

Food Pyramids

• A food pyramid is designed to show the organisms in an ecosystem, grouped by their feeding position or trophic level (1st=prod, 2nd=herbivores, etc)

• Both food chains and food pyramids show that only 10% of the energy at one trophic level makes it to the next trophic level (from the 2nd law of thermodynamics).

Primary Productivity

• Therefore, the ecosystems with the most productive producers have the most levels (ex. rain forest)– In most cases, there are only

3-4 levels.– End of 3.2

• The rate at which new organic material is created in an ecosystem by producers is called the Primary Productivity

• The more energy entering the food chain (from producers), the more that can pass up through the levels (only 10% moves up at each level), and as result, the more levels there can be.

How do nutrients cycle?

• Energy follows a ONE-WAY path– Sun living organisms heat atmosphere

• Matter CYCLES through living organisms endlessly

• Biogeochemical cycles– Water– Carbon and Oxygen– Nitrogen

Water Cycle

Carbon and Oxygen Cycle

Nitrogen Cycle

Niches

• Niches vs Habitats– A habitat is the location where a species

lives. • Ex. tall grassland/prairie

– A niche includes all of the species’ requirements plus its role in the ecosystem. It is determined by all the the abiotic and biotic factors relevant to the species.

• Ex. Top predator in prairie areas where gophers live, and the temperature is never below freezing.

Niche differences

• Organisms can be identified as either– Generalists

• Organisms with a broad niche• Eat lots of types of food• Live in many types of environments• Ex. house mice

– Specialists• Organisms with a narrow niche• Eat a narrow range of food items• Live in few, specific types of habitats• Ex. panda bear

Mutualism

• Mutualism occurs when both species benefit– Rhinos and oxpeckers

– trees and mycorrhizae,

– ants and acacia

– Termites and protist

– Pollination (Yucca and yucca moth)

Parasitism– one organism feeds on/lives on another

species– typically host is bigger than parasite– parasites usually do not kill host (weaken

them)– parasites need host for food, shelter, etc.– ex. fleas on dog, tapeworm in human,

mistletoe, lamprey

Commensalism

• Commensalism occurs when one species benefits, and the other neither benefits, or is harmed

• examples:– clownfish and

anemones

– epiphytes and trees

– Cattle egrets and ungulates

Predation

• Predation - one organism feeds upon the other– predator usually bigger than prey– ex. lion eating zebra

Prey Strategies

Competition

• When two species use the same resources, they are said to compete and their interaction = competition.– ex. lions and hyenas compete for food in

Africa

• Competition does not necessarily involve contact; interaction may be only by means of effects on the resources.

• No two organisms can occupy exactly the same niche at the same time

What determines where species can live?

• All species have requirements for many factors/conditions. – Abiotic factors – non-living factors; ex.

temperature, precipitation, pH– Biotic factors – other species; ex. prey

species, competing species

• For each of these factors, species exhibit a range of tolerance. – For example, a fish species may only be

found within a pH range of 4.5 to 6 in lakes.

Biomes

• A major terrestrial community that is found in different areas with similar climate is called a biome. A biome’s structure and appearance are similar throughout its distribution.

• The world’s biomes are tropical rain forest, tropical dry forest, temperate woodland and shrubland (Chaparral), temperate deciduous forest, boreal/coniferous forest (taiga), desert, temperate grassland, tropical grassland (savanna), and tundra.

Biome distribution

Freshwater Habitats

• These habitats are distinct from both marine and terrestrial habitats and are very limited in area.– make up about 2% of earth’s surface– can be divided into

• Flowing water (rivers) standing water (ponds and lakes) and wetlands (seasonal coverage)

Freshwater Habitats• Estuaries

– These are very important for• Breeding grounds for fish• Filtering water

– Very productive ecosystems!– Disappearing fast (flat land near the ocean)

Ocean

• 75% of earth’s surface

• Continental shelf - shallow ocean waters - smallest area; large number of species (kelp forests)

– Intertidal zones• Along our coast

• Species can tolerate being in and out of water

• Sea stars, algae, sea anemones

– Coral Reefs• The “rain forests” of the ocean

• High diversity

• In tropical waters

Ocean

• open sea surface - contains plankton (free-floating microscopic organisms), bacteria, algae, fish larvae; responsible for 40% of world’s photosynthesis

• Benthic zone - deep sea waters - below 1000’ feet animals adapted to dark; some blind/bioluminescent

What happens when ecosystems are disturbed?

• When a disturbance impacts an ecosystem, it recovers through a process known as succession.

• Succession on newly formed habitat is called primary succession. – No remaining organisms or soil– Examples, lava flow, sand dune, glacier

retreat– It can take 1000+ years from sand dune to

forest.