Ecology

Part 2

• Ecology is the study of the relationship of organisms to their environment. Ecosystems are physically distinct, self-supporting systems of interacting organisms & their environment. Ecosystems are composed of communities of organisms & the abiotic, or nonliving, factors in the environment, such as sunlight, soil, & water.

• Within an ecosystem, an organism occupies a physical region called its habitat. It also has a specific niche, or way of life.

• Abiotic factors play an important role in determining where organisms live. Organisms depend upon a continuous supply of recycled nutrients, such as nitrogen & carbon. Organisms can be carnivores, herbivores, or omnivores.

• All organisms occupy a trophic level, & all are members of a specific food chain. Permanent, close relationships between different species are called symbiosis. Organisms respond to regularly occurring phenomena in patterns called Circadian Rhythms.

IMPORTANT TERMS forECOSYSTEMS

• Biotic factors – living componentsAbiotic factors – nonliving componentsCommunities – several populations interacting

• Populations- group of individuals of the same speciesHabitats – where an organism livesNiches- the specific role of the organism in its habitat

BIOTIC RELATIONSHIPS • Competition –

2 or more organisms striving for the same resources

• Predators – captures & feeds on other (prey)

• Symbiosis –relationship in which 2 organisms live closely together

1)Mutualism – both benefit

2)Commensalism – one benefits, the other is neither harmed nor helped

3)Parasitism –one benefits, the other is harmed

• Circadian Rhythm – cycle of sleep & wakefulness

• Diurnal – day-active• Nocturnal – night-active • Hibernation – dormant in

the winterEstivation – dormant in the summer

Community Ecology

• Limiting factor – any abiotic factor that restricts the numbers, reproduction, or distribution of organisms – ex. = water, light, phosphorus

• Range of tolerance – optimal range of conditions for organisms – ex. = temperature, sunlight, pH

SUCCESSION & BIOMES

• The biological communities of the world are constantly changing. Many of these changes involve ecological succession, or the replacement of 1 group of species by another group that is more adapted to life in a given area.

IMPORTANT TERMSfor ECOLOGICAL SUCCESSION

• Seral community – intermediate community – prevents its own regenerationClimax Community –stable, permanent community

• Primary succession –life has not been there before (bare rock)

• Pioneer species –1st organism to an area (usually lichens)

• Eutrophication –adding nutrients to an ecosystem

• Secondary succession –changes in a community where life has been before (old field succession – soil is usually intact)

Two types of ecological succession

• Primary succession takes place where no community existed before. Secondary succession takes place on land that has previously supported communities. During succession land is occupied by a number of seral communities before a climax community finally becomes established.

• Large areas of similar climate & vegetation are called biomes. Tundra, boreal forests, deciduous forests, grasslands, tropical rain forests, & deserts are the major terrestrial biomes. Two biomes make up the aquatic world: the marine & freshwater. Estuaries are special aquatic communities.

Effects of latitude & climate

• Latitude & climate are the 2 primary factors that determine the type of ecosystem present. Winds, ocean currents, & the greenhouse effect can affect the type of climate present in an area.

TERRESTRIAL BIOMES

Biome –area of similar climate, & vegetation

Tundra

Boreal (Coniferous) Forest or Taiga

Temperate Deciduous Forest

Chaparral

Temperate Grasslands

Savanna

Desert

Tropical Dry Forest

Tropical Rain Forest

AQUATIC ORGANISMSPlankton: floaters - Phytoplankton

(plant), Zooplankton (animal), Ultraplankton/nanoplankton (photosynthetic bacteria)

Nekton: swimmers - fish, turtles, whales

Benthos: bottom dwellers (octopus, oysters)

Decomposers: breakdown organic compounds (mostly bacteria)

Freshwater ZonesLittoral zone (near shore, shallow, with rooted

plants - lots of biodiversity)Limnetic zone (open, offshore area, sunlit - main

p.s. portion of lake - lots of O2)Profundal zone (deep, open water, too dark for

photosynthesis - low O2)Benthic zone (bottom of lake, nourished by

dead matter - lots of decomposers).

Oligotrophic –little nutrients in the water

Eutrophic – lots of nutrients in the waterEstuary – where rivers meet the oceans

Marine ZonesIntertidal Zone – between high & low tideCoastal zone (from shore to continental shelf -

contains 90% of all oceanic species)Open sea - a) euphotic zone - low nutrients, high p.s., high

O2 b) bathyal zone - no p.s. - lots of migration c)

abyssal zone - dark, lots of nutrients, low O2

Open Sea zone – between continents

POPULATIONS IN ECOSYSTEMS

Populations are composed of individuals of the same species living in the same area. The maximum rate of reproduction for a population is its biotic potential. A population allowed to reach its biotic potential would soon cover the earth. The growth of populations is regulated by the environment’s limiting factors such as rainfall, light, food, space.

When a population establishes itself in a new area, it grows slowly at first. The population then enters an exponential phase of growth in which its number doubles at decreasing intervals. Exponential growth ceases when the carrying capacity of the environment is reached. The carrying capacity is determined by limiting factors that restrict population growth. Some limiting factors depend on the population’s density; some are independent of density.

Changes in populations are calculated by subtracting the number of deaths & emigrants from the number of births & immigrants. Population crashes & explosions are dramatic changes in the size of populations.

Growth = (Births + immigrants) – (Deaths + emigrants)

The human population is currently in its exponential phase of growth. The number of humans now doubles about every 35 years. Providing for this growing population is one of the major problems facing the modern world.

IMPORTANT TERMSfor POPULATION GROWTH

Biotic potential – maximum growth rateLag phase – period of slow growthExponential Growth – the number of

individuals repeatedly doublesExponential Phase – period during which the

population doubles

J-Curve – combination of exponential growth & lag phases

Stabilization Phase – population size levels offCarrying Capacity – maximum number of

individuals the environment can support

S-Curve – combination of lag, exponential, & stabilizing phases

Limiting factors –environmental elements that stabilize population size & keeps species from reaching their biotic potential

Population Density – number of individuals in a given area

Density-Independent Factors –elements that affect population size that are not affected by the number of individuals in the population (tornadoes, floods, hurricanes)

Density –Dependent Factors –elements that affect population size that ARE affected by the number of individuals in the population (space, food, diseases)

Saw-Tooth Curve –pattern formed by periodic growth & decline in a population

Birth Rate –number of births per yearDeath Rate –

number of deaths per yearGrowth Rate – rate at which population

changes

What are age-structure pyramids? Diagram that

shows the percentage of the population at each age level in a population

Demographic transition – as countries become industrialized, they have a decline in death rates followed by declines in birth rates