Obj. Describe how ecosystems change over time
Obj. Explain how new communities arise in areas
Obj. Compare & Contrast pioneer communities & climax
communities
Ecological Succession
It can many years for a forest to grow. Sometimes, it is easy to think of a forest as something that has always been there. But like everything else, nothing happens overnight and because of this a forest go through a process of growth and development.
Steps in Primary Succession
What is primary succession? Ecological succession that begins in a place that does not have soil.
Step 1 - Pioneer community moves in to new area
(usually hardy organisms that can survive drought, extreme heat & cold and other harsh conditions)
examples - lichen are organisms made up of a fungus and green algae or a cyanobacterium living in a mutualistic relationship.
Step 2 - Moss & ferns appear (can thrive even in extremely poor soil; as they die, their decomposed bodies add humus to soil) Insects and other small animals appear
Step 3 - As soil layers thicken, its ability to hold water improves. (grasses, wildflowers, butterflies, bees & caterpillars) What happens when these organisms die?
Step 4 - Thicker, richer soil supports the growth of shrubs and trees. (More insects, birds, mammals & reptiles move into the area.)
Secondary Succession
Succession that begins in a place that already has soil and was once the home of living organisms.
Climax Community
When a community has reached the final stage of ecological succession.
How long does it take?
Primary succession begins in places with no life at all, so it could take hundreds or even thousands of years for a pioneer community to develop into a climax community.
Secondary succession is a shorter process, but could still take a century or more.
Comparing Pioneer and Climax Communities
- Pioneer communities are simple
-- contain only a few species (simple food chain)
- Climax communities are much more complex, with thousands of species (more complicated food webs)
Section 19-2 (land Environments)
Obj. Explain how climate influences land environments
Obj. Describe the six biomes that make up land enviroments
on earth
Obj. Compare and Contrast the adaptations of plants and
animals found in each biome
Temperature
- the sun supplies life on earth not only with light energy for photosynthesis, but also heat energy for warmth.
(The temperature of a region is regulated by how much sunlight reaches it.)
Latitude
- as the earth rotates around the sun, it tilts on its
axis, this causes changes in the amount of energy
that "hits" it.
- not all parts of the earth receive the same amount of
energy from the sun
-- the nearer a region is to the south/north pole, the
higher the latitude (the smaller the amount of
energy it receives from the sun, and the colder the
climate)
-- the nearer a region is to the equator, the lower the
latitude (greater amounts of energy it receives from
the sun, and the hotter the climate)
Inquiry question
What effect does the tilt of the earth have on temperatures for regions near the equator?
Elevation
A region's elevation (or distance above sea level) also has an impact on temperature. Temperatures drop as you go higher in elevation.
ex. The climate on a mountain will be cooler that the climate at sea level
Elevation also has an impact on plant growth.
Are higher elevations more favorable for plant life?
Hmmm, what do you think?
Precipitation
- the amount of water that condenses and falls in the form of rain, snow, sleet, hail, fog.
Did you know that warm air rises?
Okay, did you know this? Cold air sinks.
The Rain Shadow Effect
The presence of mountain ranges has an effect on rainfall patterns. Can you explain what happens?
It's know as the "Rain Shadow Effect"
The Rain Shadow Effect
Land Biomes
- large geographic areas that have similar climates and ecosystems are called biomes.
six most common biomes
- Tundra, Taiga, Temperate forest, Tropical rain forest, Grassland, Desert
Tundra
- at latitudes surrounding the north pole
- receives little precipitation
- ice-covered most of the time
- dry (< 25cm precip per year) & tree-less
- sometimes called "cold desert"(winters 6-9 months long)
- long nights during winter months (temps. to -40C)
- short cold summers (sun never sets)
-- only top few inches of soil thaw; below this level
is a layer or permanently frozen soil (permafrost)
- soil is poor with nutrients
Taiga
- between latitudes 50 degrees N & 60 degrees N
-- stretches across Canada, northern Europe, Asia
- World's largest biome
- called the "northern coniferous forest"
-- contains cone-bearing evergreens (pines, firs,
hemlocks, spruces & cedars)
- long, cold winter
- 35 - 40 cm precip/year (mostly snow)
- grounds thaws completely (no permafrost) making it
possible for trees
Temperate Deciduous Forest
- found in both the northern and southern hemisphere
-- latitudes below 50 degrees
- 4 seasons per year
- 75 -300 cm of precipitation per year
- temperatures < 32F during winter & > 88F durng summer
- deciduous trees dominate (lose their leaves every year)
Layers of Vegetation
canopy, understory, forest floor
Tropical Rainforest
- >200cm or rainfall per year
- contains more than 1/2 of all of the species that exist
on earth
- hot, humid environment (ever been inside a greenhouse?)
Grassland
- betwen 25 - 75cm precipation/year
- dry season, when little or no rain falls (also prevents
the development of forest
- variety of names (Plains of North America, Steppes of
Asia, Veldts of Africa & Pampas of South Africa)
- grass plants have extensive root system, called sod
that absorb water (when it rains); can withstand
droughts
- soil is rich and fertile
Desert
- driest biome on earth (<25cm precip/year)
- most are covered with a thin, sandy or gravelly soil
that contains little humus
- what adaptations do organisms living in this biome
need?
Section 19-4 (Water Environments)
Freshwater Biomes
- limiting factors are the amount of salt in the water or salinity, dissolved oxygen and sunlight
- fresh water contains little or no disolved salts (low salinity)
Rivers & Streams
- the faster the stream, the clearer the water and the higher the oxygen content
Lakes and Ponds
- a lake or pond forms when a low place in the land fills with rainwater, snowmelt, or water from a stream.
-- little or no movement of water
-- contains more plant growth than flowing-water environments
- a pond is a shallow body of water
-- as such, sunlight penetrates to bottom, making water
warmer & promoting the growth of plants and algae
--- high in nutrients
- a lake is larger and deeper than a pond
-- most plant growth is limited to shallow areas along
the shoreline
-- plankton - microscopic algae, plants & other
organisms live in lakes
Salt Water Biomes
- 95% of the water on the surface of the earth contains high concentrations of salt
-- salt water biomes include oceans, Great Salt Lake
Estuaries
- the area where a river meets an ocean and are located near coastlines and border the land
- extremely fertile
Seashores
- all of the earth's landmasses are bordered by ocean water
- the fairly shallow waters along the world's coastline contain a variety of saltwater ecosystems, all of which are influenced by the tides and by the action of waves (gravitational pull of the moon causes the tides to rise and fall twice a day)
- the intertidal zone is the portion of the shoreline that is covered with water at hight tide and exposed to the air during low tide
two types - sandy beaches & rocky shores
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