1. Chapter III: Community Ecology
I. Distribution of Organisms in the Biosphere:
Climate: the long term weather patterns of a region on Earth.
The long term weather patterns are affected by location on the Earth, the latitude (distance from the
equator), and elevation (height above sea level), and distance from body of water.
II. Factors Affecting Abiotic Conditions:
1) Solar Energy:
Responsible for the average temp. at various locations throughout Earth.
Those areas near the equator are warmer because the sun’s rays hit them directly.
The tilt of the Earth creates the seasons in most areas of the world.
2) Winds & Current:
Movement of warm and cold air masses create winds. As warm air masses near the equator
move to cold regions near the poles, they cause wind patterns that affect the climate.
Wind patterns drive the movement of ocean currents, which in turn are involved in circulating
heat.
The ocean’s water has a large heat capacity and absorbs solar energy. It releases this solar energy
slowly
Where oceans meet continents, airflow is disrupted. Warm moist air from the ocean rises over
mountains and cools, releasing large amounts of precipitation.
On the far side of the mountain, a rain shadow exists where dry mountain air warms as it descends
and releases little moisture.
Climatograph shows the monthly changes in temp. and precipitation throughout a year.
Precipitation and temp. are the most influential determiners of the types of plants and organisms
that exist in a community.
III. World Biomes;
Different areas of the world may share similar abiotic factors and as a result, will have similar but
distinct ecosystems.
Biome: terrestrial ecosystems that have similar environments but exist over a wide area of the
world. There are 8 biomes world wide.
1) Tundra: very little precipitation. Small, slow growing plants survive the harsh conditions.
Growing season is very short, about 8 weeks.
Permafrost, permanently frozen soil, is often present within 1 m of the surface.
2) Boreal Forest/Taiga: south of the tundra. More precipitation than in the tundra, but air is dry
during the winter.
Conifers dominate this biome. They limit the number of other species that
can thrive in the taiga. They form canopies, or leaf covers, so that sun light
cannot reach the other plants closer to the ground.
2. 3) Temperate Deciduous Forest: south of the taiga. Warmer temp. and abundant rain gives rise to
huge forests of broadleaf trees. Fallen leaves create a fertilizer
rich ground cover for other plants to grow in the understorey.
Many bugs and insects feed off the fertile ground cover and in
turn become prey for other large organisms.
4) Temperate Rainforest: the rarest of the biomes.
Coastal mountains cause moist ocean air to rise and cool, dropping
between 2-3.5m of rain annually and mild conditions.
The large amount of ppt. causes the ground cover to rot easily, providing
fertilizer for shrubs and bushes to grow.
5) Grassland: rainfall 25-75cm/year. Not enough for tree growth. Grasses are able to grow rapidly
however.
Savannas support a large number of herbivores.
6) Tropical Rainforest: receive between 2-4.5m of rain and temp. remains fixed at 30-350C.
This biome is believed to contain ½ the world’s terrestrial organisms. A
10km2 region of tropical rain forest could contain as many as 750 plant
species.
7) Desert: receive less than 25cm of rain annually. Plants are small and adapted to have waxy top
layers to keep water from evaporating. Most organisms are nocturnal and have large ears
to improve heat loss.
8) Polar Ice: has permanent ice. Herbivores are non-existent in this biome. Predators take
advantage of the marine ecosystem for survival.
Biogeoclimatic Zones of BC:
BC is Canada’s most ecologically diverse province. Covers 95 million hectares. Has some of the
wettest, driest, warmest, coldest locations, including rainforest, grassland, desert. Due to this extreme
variety, there is now a new classification system: Biogeoclimatic Ecosystem Classificaiton (BEC).
BEC describes 14 distinct ecological zones in BC. The zones are named after the predominant plant in
the region.
We are the only area in the world with such a diverse ecology.
IV. Environmental Adaptation:
Adaptation: any genetic trait that improves an organism’s odds of surviving and reproducing.
= Good Fitness (ABILITY TO SURVIVE & REPRODUCE)
****Organism is born with/without well adapted traits. Can’t change
Natural Selection: a process that favours the survival of the organism with traits that make them better
adapted to the environment. Abiotic as well as biotic factors can influence natural
selection.
Natural selection can also affect prey species that must adapt in order to survive.
Camouflage is one method. Warning colours also advertise that some prey are
poisonous.
Mimicry is an adaptation where one animal resembles another species that is
poisonous to avoid being eaten or to attract prey.
Co-evolution is the adaptation of two species in response to each other.
3. Biodiversity: the variety and variation among organisms within a given ecosystem or biome.
Biodiversity is closely linked to primary productivity – A measure of the available
energy provided by the producers in an ecosystem. The greater the primary productivity,
the greater the biodiversity.
Extinction: where a species is gone completely from the earth or the numbers are so low that
reproduction is impossible.
Extirpation: local extinction, where a species ceases to exist in one area but is still prevalent in another.
Keystone Species: species whose presence plays an important role in determining the types and numbers
of other species in particular communities.
V. Community Interactions:
Niche: the overall role of an organism in a community, including the range of biotic and abiotic
conditions that the organism can tolerate.
Competition occurs when two organisms make use of the same resources so that their niches overlap.
Interspecific Competition: competition between species.
Intraspecific Competition: competition within the same species. This is more intense
form of competition.
Resource Partitioning: different species have different traits that allow them to use a resource at
different time. (Ex. Hawks hunt mice in the day time whereas owls hunt mice
during the night).
Adaptive Radiation: where species adapt differently to changes to the environment. The species become
specialized to exploit smaller parts of a niche. (Ex. Finches’ beaks on the
Galapagos Island).
Foreign Species: an organism that is not native to a particular ecosystem.
Foreign species often out-compete the native species and can cause widespread
devastation.
Ecological Succession: the gradual change in the types of plants that represent the structure of a
community.
Pioneer species arrive first and colonize the new environment. These pioneer
species changes the environment and creates an acceptable condition for other
species. Over time, other plant species that are more suitable to the environment
overtake the pioneer species.
There are two types of succession: 1) Primary Succession: begins in area lacking in life and
nutrients such as exposed rocks.
Once changes occur to a point where a
stable ecosystem can thrive, this is now
called a climax community.
2) Secondary Succession: begins in area where there is already
soil and some life, but was dramatically
