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 Omnivore

(eats plants)

Carnivore

(eats both) (eats meat) –

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

pyramid.

food chain, food web, or food

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

Food Web

links 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

(1 st =prod, 2 nd =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 2 nd law of thermodynamics).

Primary Productivity • 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.

• 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

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.