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 for ECOSYSTEMS Biotic factors – living components Abiotic factors – nonliving components Communities – several populations interacting Populations- group of individuals of the same species Habitats – where an organism lives Niches- 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 winter Estivation – 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 TERMS for ECOLOGICAL SUCCESSION Seral community – intermediate community – prevents its own regeneration Climax Community – stable, permanent community Primary succession – life has not been there before (bare rock) Pioneer species – 1 st 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 ORGANISMS  Plankton: 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 Zones  Littoral 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 water  Estuary – where rivers meet the oceans

Marine Zones  Intertidal Zone – between high & low tide  Coastal 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 TERMS for POPULATION GROWTH  Biotic potential – maximum growth rate  Lag phase – period of slow growth  Exponential Growth – the number of individuals repeatedly doubles  Exponential Phase – period during which the population doubles

 J-Curve – combination of exponential growth & lag phases  Stabilization Phase – population size levels off  Carrying 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 year  Death Rate – number of deaths per year  Growth 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