Transcript Chapter 4

Chapter 4
Ecosystems and Communities
Weather vs. Climate
• Weather: day to day condition of Earth’s
atmosphere at a particular time and place.
• Climate: refers to the average, year-afteryear conditions of temperature and
precipitation in a particular region.
The Greenhouse Effect
• Carbon dioxide, methane, water vapor, and a
few other greenhouse gases trap heat energy
and maintain Earth’s temperature range.
• These gases trap the heat energy of sunlight
inside earth’s atmosphere.
• This process is known as the greenhouse effect.
• If these gases were not present in the
atmosphere, Earth would be 30°C cooler than it
is today.
The Effect of Latitude on Climate
• Latitude: the distance north or south of the
equator of a point on the earth's surface.
– The equator receives the most direct sunlight.
• As a result of differences in latitude and
thus the angle of heating, Earth has 3
main climate zones:
– Polar
– Temperate
– Tropical
Polar Zones
• Cold areas where the sun’s rays strike
Earth at a very low angle.
• These zones are located in the areas
around the north and south poles,
between 66.5° and 90° North and South
latitudes.
Temperate Zones
• Sit between the polar and tropical zones.
• These zones are characterized by a
change in temperature over the course of
a year.
• The reason: they are more affected by the
changing angle of the sun causing ranges
in heat from hot to cold, depending on the
season.
Tropical Zone
• Located near the equator between 23.5°
North and 23.5° South latitudes.
• The tropics receive direct or nearly direct
sunlight year-round, making the climate
almost always warm.
What shapes and ecosystem?
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Biotic and Abiotic Factors
The Niche
Community Interactions
Ecological Succession
Biotic and Abiotic Factors
• Biotic factors: the biological influences on organisms
within an ecosystem.
– The ecological community
• Abiotic factors: physical, or nonliving, factors that shape
ecosystems.
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Temperature
Precipitation
Humidity
Nutrient Availability
• The biotic and abiotic factors determine the survival and
growth of an organism and the productivity of the
ecosystem in which the organism lives: habitat.
The Niche
• A niche is the full range of physical and
biological conditions in which an organism
lives and the way in which the organism
uses those conditions.
• An organism’s niche includes:
– Type of food
– How it obtains food
– Which other species use the organism as
food.
Community Interactions
• Competition
• Predation
• Symbiosis
Competition
• Competition: when organisms of the same
or different species attempt to use an
ecological resource in the same place and
at the same time.
– Resource: any necessity of life.
• Competitive exclusion principle: states that
no two species can occupy the same
niche in the same habitat, at the same
time.
Predation
• Predation: an interaction in which one
organism captures and feeds on another
organism.
– Predator: the organism that does the killing
and eating.
– Prey: the organisms that is eaten.
Symbiosis
• Symbiosis: any relationship in which two species
live closely together.
• 3 main classes of symbiosis:
– Mutualism: both species benefit.
• Termite and protist
– Commensalism: one species benefits and the other is
not affected
• Barnacles and whales
– Parasitism: one species benefits and the other is
harmed
• Tapeworm and pig
Termite Gut
Whale and Barnacles
Tapeworm
Ecological Succession
• Ecosystems are constantly changing in
response to natural and human disturbances.
• As an ecosystem changes, older inhabitants
naturally die out and new organisms move in,
causing further changes in the community.
• This series of predictable changes that
occurs in a community over time is called
ecological succession.
There are 2 Types of Ecological
Succession
• Primary Succession
• Secondary Succession
Primary Succession
• Occurs on land where no soil exists.
• Ex: Occurs on the surfaces formed as volcanic eruptions build
new islands or cover the land with lava rock or volcanic ash.
– When it begins there is no soil, just ash and rock.
– The first species to populate the area are called pioneer
species.
– The pioneer species on volcanic rock are often lichens.
– Lichens are organisms that are formed from the mutualistic
relationship between algae and fungi.
– As they grow they break up the rock.
– When they die they add organic matter to help form the soil
on which plants can grow.
Secondary Succession
• Follows a disturbance that changes an
existing community without removing soil.
• Occurs when land cleared for farming or
mining is abandoned, or when wildfires
burn woodlands.
– Certain plants have adapted to a regular cycle
of fire and re-growth.
– Their seeds won’t sprout unless exposed to
fire.
Secondary Succession in an
Uncultivated Field
Biomes
• A biome is a complex of terrestrial (land)
communities that covers a large area and
is characterized by certain soil and climate
conditions.
The Major Biomes
• There are at least 9
biomes scientists
recognize:
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Tropical rain forest
Tropical dry forest
Tropical savanna
Temperate grassland
Desert
– Temperate woodland
and shrubland
– Temperate forest
– Northwest coniferous
forest
– Boreal forest (taiga)
– Tundra
Aquatic Ecosystems
• Aquatic ecosystems are determined
primarily by the depth, flow, temperature,
and chemistry of the overlying water.
• There are 3 categories of aquatic
ecosystems:
– Freshwater
– Estuaries
– Marine ecosystems
Freshwater Ecosystems
• Flowing-Water Ecosystems
• Standing-Water Ecosystems
• Freshwater Wetlands
Flowing-Water Ecosystems:
• Rivers, streams, creeks, and brooks
• Organisms that live there are well-adapted
to the rate of flow.
Standing-Water Ecosystems:
• Lakes and ponds
• Relatively still waters provide habitats for
many organisms that would be quickly
washed away in flowing water:
Freshwater Wetlands:
• An ecosystem in which water either covers
the soil or is present at or near the surface
of the soil for at least part of the year.
• Bogs, marshes, swamps
Trees in a Marsh
Estuaries
• Wetlands formed where rivers meet the sea.
• They contain a mixture of freshwater and salt
water.
• Examples:
– Salt Marshes: temperate-zone dominated by salttolerant grasses above the low-tide line, and by seagrasses underwater.
– Mangrove Swamps: coastal wetlands that are found
in tropical regions, including southern Florida
(everglades) and Hawaii.
• The Dominant plants are salt-tolerant trees, collectively
called mangroves.
Estuary
Marine Ecosystems
• Zones based on depth:
– Photic zone: well-lit upper layer of the ocean, where
photosynthesis can occur (depth of about 200
meters).
– Aphotic zone: below the photic zone, permanently
dark area where only chemosynthetic autotrophs are
the producers.
• Zones based on distance from the shore and depth:
– Intertidal zone
– Coastal zone
– Open Ocean
Intertidal Zone
• Organisms in the intertidal zone are
exposed to regular extreme changes in
their surroundings.
• Once or twice a day they are submerged
in seawater, while the remainder of the
time they are exposed to sunlight, air, and
temperature changes.
• There are many different types of intertidal
communities.
Intertidal Zone
Coastal Ocean
• Extends from the low-tide mark to the outer edge
of the continental shelf, the relatively shallow
border that surround continents.
• The continental shelf is often shallow enough to
fall mostly or entirely in the photic zone, so
photosynthesis can occur throughout this depth.
• Kelp forests: a collection of giant brown alga
(seaweed) that can grow as quickly as 50
cm/day.
• Coral Reefs: found in the warm, shallow water of
tropical coastal oceans.
Kelp Forest
Coral Reefs
Open Ocean (Oceanic Zone)
• Begins at the edge of the continental shelf
and extends outward.
• It is the largest marine zone.
• Ranges about 500 m deep – > 11,000 m
• Organisms in the deep ocean are exposed
to high pressure, frigid temperatures, and
total darkness.
• Benthic zone: ocean floor