Ecology

Living vs. Nonliving The environment is made of both living and

nonliving things Biotic factors are all the living things that

directly or indirectly affect the environment Ex: organisms Abiotic factors are physical and chemical

factors that affect the ability of organisms to live and reproduce

Ex: intensity of light, temperature, water, soil and rock, minerals, gases, pH

If an abiotic factor is in short supply, it is a limiting factor

Limiting factors determine what types of organisms can exist in an environment

Ex: low levels of light may inhibit plant growth Ex: low (or high) temperatures may affect an

organism’s enzymes Ex: low oxygen levels in lakes affect how many

fish can live there

Ecology Ecology: the study of the interactions among

organisms and their interrelationships with the physical environment

Environment: an organism’s physical, chemical, and biological surroundings

All living things are dependent on each other and the nonliving environment

Ecological Organization Population: all the members of a species

inhabiting a given location at a specific time Community: all the interacting populations in an

area Ecosystem: the living community and the

physical environment functioning together as an interdependent, self-sufficient, and relatively stable system

Biosphere: the portion of Earth in which life exists

Ecosystems Ecosystems are self-sustaining if they: 1. have a constant source of energy 2. have a living system capable of turning this

energy into organic compounds 3. have mechanisms to cycle and recycle

materials between organisms and the environment

The Sun is Earth’s energy source, and plants incorporate solar energy into glucose

Nutrition Remember! Autotrophs make their own food,

and heterotrophs need to eat other organisms Saprophytes (decomposers): heterotrophs that

live on dead matterEx: fungi and bacteria

Herbivores: animals that eat only plants Carnivores: animals that eat other animals Omnivores: animals that eat both plants and

animals

Predators hunt and consume prey Scavengers eat animals that have been killed by

other animals

Material Cycles The oxygen cycle involves photosynthesis and

cell respiration

Oxygen in air and water

Water

Cellular respiration and burning

Photosynthesis

The carbon cycle shows how carbon moves from the environment, into organisms, and back into the environment

CO2 in air and water and calcium

carbonate in soil

Organic compounds made in animals

Plants eaten by animals

Organic compounds made by plants

Respiration and decay

Burning, respiration,

decay

Photosynthesis

The water cycle is a very important limiting factor in any ecosystem

Evaporation: liquid water becomes water vapor Transpiration: evaporation of water from the

leaves of plants through stomata Condensation: water vapor becomes liquid water Precipitation: liquid or frozen water falls back to

the ground

Atmospheric Condensation (humidity, water vapor, fog, clouds)

Condensation

Water Table (ground water, oceans, lakes, ponds, rivers, wetlands)

Evaporation

Transpiration

Precipitation

Energy from the Sun

Cell respiration

and excretion

Rain, Snow, Sleet, Hail

The nitrogen cycle recycles the nitrogen necessary for the production of proteins

Nitrogen gas from the atmosphere is converted into nitrates by nitrogen-fixing bacteria

Plants use nitrates to make proteins Animals eat plants and convert plant proteins

into animal proteins Wastes and dead bodies are broken down by

decomposers, and ammonia is released Nitrifying bacteria convert ammonia into nitrates Denitrifying bacteria break down nitrogen

containing compounds and release nitrogen gas

Free nitrogen in air

Nitrates

Plant proteins

Animalproteins

Decomposers

Ammonia

Nitrogen-fixing bacteria

Animal and plant wastes

Denitrifying bacteria

Energy Flow The food chain shows how energy flows from

organism to organism Food chains start with producers (green plants)

that convert the Sun’s energy into organic compounds that can be used by other organisms

Consumers that feed directly on plants are primary consumers

Secondary consumers feed on other consumers Decomposers return chemicals to the

environment for reuse

Sun

GrassCricket

Frog

SnakeHawk

Food webs are many interconnected food chains

Food webs are more accurate because organisms have evolved to eat more than one type of food

The direction of the arrows in a food chain or web shows the direction of energy flow

Pyramids A pyramid of energy shows the amount of usable

energy available at each feeding level The producers always have the most energy Only 10% of the energy available at one level

gets transferred to the next The other 90% is mostly lost as heat

Grass

Cricket

Frog

Snake

Hawk

Most Energy

Least Energy

The pyramid of biomass shows how many organisms can be supported at each level

The carrying capacity is how many members of a species can be supported by an ecosystem

There are always more producers than consumers

Grass– 1 million

Cricket—100,000

Frog—10,000

Snake—1,000

Hawk—100

Symbiotic Relationships A symbiotic relationship is one in which

different organisms live in close association Commensalism: one organism is benefited and

the other is neither helped nor hurt (+, 0) Ex: barnacles on whales Mutualism: both organisms benefit (+,+) Ex: flowers and bees Parasitism: the parasite benefits and the host is

hurt (+,-) Ex: fleas on a dog

Biodiversity Biodiversity is the variety of different organisms

in an ecosystem Biodiversity increases the stability of the

ecosystem and increases the possibility of medical discoveries

Ex: many new medicines come from rainforest plants

Succession Succession: the replacement of one community

with another until a stable stage is reached The stable stage is a climax community Succession begins with pioneer organisms,

which are the first livings things in a given area Each new community modifies the environment

Makes it more unfavorable for themselves, but more favorable for the next community

Plant species are called flora Animal species are called fauna

Climax communities are self-perpetuating communities in which the populations remain stable and exist in balance with each other and the environment

A climax community will continue until a catastrophe or major change in the biotic or abiotic factors destroys it

Ex: forest fires, abandoned farms After the catastrophe, succession begins again

May end with a different climax community or the same one again

Habitats Habitat: particular area in the ecosystem where

a specific plant or animal lives Different species may need to use the same

resources in the habitat, so competition occurs The more similar the requirements, the more

intense the competition A niche is the role a species plays in its

environment Competition usually limits organisms to one

species per niche

Biomes A biome is the most common climax ecosystem

that will form in a geographic region Biomes can be terrestrial (land) or aquatic

(water)

Tundra The tundra is found in the northernmost regions

of North America, and Europe Very little precipitation (10 inches/year) Most of the ground remains permanently frozen

(permafrost) Trees cannot grow because the permafrost does

not allow for deep roots Most of the plants are mosses, grasses, and

lichens

The tundra has short, warm summers and long cold winters

Animals need to be adapted to the cold Ex: caribou, snowy owls, musk oxen

Taiga The taiga is found just south of the tundra in

North America, Europe, and Asia Receives more precipitation than the tundra The temperatures are warmer than the tundra,

so there is no permafrost The main type of tree is the conifer, which has

needles instead of leaves Winters are long and cold Animals may hibernate to avoid the winter

Temperate Deciduous Forest The deciduous forest is found in the eastern US,

Europe, and northeastern China This is the climax community of New York State Has cold winters and warm summers The main type of tree is the deciduous tree

Lose their broad leaves in the autumn Deciduous trees lose their leaves to prevent

water loss in the winter when water is limited

Soil in the forest is very richThe fallen leaves decompose and return nutrients to

the soil Examples of fauna: squirrels, deer

Tropical Rainforest The tropical rain forest is the most complex

biome on Earth All tropical rain forests are found near the

equator Receives 160 inches of rain each year

Rains nearly every day The abundant rain allows trees to reach over 200

feet tall

Grasslands Grassland biomes exist in both temperate and

tropical regions Receives about 30 inches of precipitation each

year and has strong winds There are no trees because there is not enough

rain Also experience occasional droughts

Grass thrives because its roots are very deep and reach underground water

Desert A desert biome experiences more evaporation

than precipitationWater evaporates faster than it can be replenished

Deserts receive less than 10 inches of precipitation each year

Rain is often violent and heavyMay receive all 10 yearly inches in one day

Deserts experience a wide range of temperatures Very hot during the day and very cold at night

Desert plants like cacti are succulentsHave thick, fleshy stems that store waterHave shallow, sideways roots that are able to quickly

absorb rainwaterSpines protect the plant from being eaten and reflect

sunlight away from the plant Trees in the desert are short because of the lack

of waterHave very deep roots to reach underground water

Desert plants are widely spaced to reduce competition for water

Lizards and snakes have thick scales to reduce water loss

Mammals like mice and kangaroo rats rest in underground burrows during the day to avoid the heat

Marine Biome The marine biomes are in the ocean They provide the most stable aquatic

environment Absorb and hold large amounts of solar heat and

stabilize the atmosphere Supply nutrients and dissolved salts Serve as a habitat to many diverse species

Freshwater Biomes Lakes, ponds, and rivers Ponds are shallow and light can reach the

bottomPlants and phytoplankton can live in all areas

Lakes are deeper and light only reaches a certain level

Plants cannot grow in areas where there is no sunlight