Ecology: Community Distribution

Range of Tolerance for a Population

INSERT FIGURE 3-10 HERE

Limiting factor principle

– Too much or too little of any abiotic factor can limit

or prevent growth of a population, even if other

factors are at or near the ____________.

Succession: Changes in a Community over __________

Primary succession: Colonization of new land (such as after a volcanic

eruption) when ________________ is present.

Over time, region may develop into a climax community.

Secondary Succession: Gradual change in a community that has been

disturbed, but some biotic matter is present.

Examples: ______________________________

Discuss with your table partner:

What are characteristics of pioneer species (the first species that colonize a new location)?

Compare the characteristics of two different trees below and predict which would come earlier in the succession process. Predict which type of tree would tend to be more dominant in the later stage of succession. Be able to explain your answers.

Type of Tree Shade Tolerance Rate of Growth

White Spruce High Slower

Jack Pine Low Faster

Pioneer species- Able to grow in conditions without ______ , or in soil with _____________ content. Pioneer species help enrich the soil.

Example: Lichen can grow on bare rock.

In the process of succession, _______________ plants are first established and then over time species that can ______________ for resources replace these earlier species.

For example, faster growing trees that have higher light requirements may be replaced by hardwood trees.

Final mature/climax community dependent on climate.

Biomes: Large group of ecosystems that share a similar type of

climax community.

Terrestrial (Land) Biomes

Climate Background

Why is there often dew on the ground in the morning?

• Cold air is more dense, so it ___________________ _______________________. When air cools, it may not be able to hold all the water vapor and some may condense into (liquid) water.

Hot Air Cold Air

Climate Background Cont.

Why is the light at the equator more intense?

The light at the equator is most _________________, while the light strikes the earth at more of an angle at locations towards the poles. (esp. in winter when tilted away).

When a light source shines at an angle on a surface, the same amount of light is spread over a ____________, so the light is less intense.

(Fewer rays of light / unit of area)

Location of Biomes Which type of biome is located near the equator (desert,

rainforest, grasslands etc.)?

Most tropical rainforests are found near the equator.

Air at the equator generally heats up the most, because the light is most direct. (Sun most directly overhead.)

Hot air rises. As the air rises, _____________.

The cooling air can not hold as much water vapor so it comes out as rain.

Tropical Rainforest

• > 200 cm rain per year

• greatest _____________________

• low latitude biome= close to the equator

(latitude of the equator = 0 °)

Where are most deserts located? Why?

Most deserts are found at 30 ˚ N or 30˚ S.

• The air that rises at the equator generally sinks back to Earth at 30˚ N or 30˚ S.

• This air has already lost most of its moisture at the equator, and it warms as it returns to earth, making it more likely to retain any moisture.

Deserts • Less than 25 cm precipitation/year

• Many plants grow quickly to maturity after rainfall

• Cacti and other desert plants have ____________ to prevent water loss.

Grasslands • Dry season doesn’t support forests

• 25-75 cm of rainfall

• Very _____________________ because of a build-up of nutrients during the cold/dry season.

• Largest terrestrial biome

Temperate Forests • Moderate temperatures

• 70-150 cm of rainfall

• Dominated by deciduous trees

(_______________________)

High Latitude Biomes = Closer to the Poles

Taiga • Northern coniferous forests.

(cone bearing trees such as pines, firs)

• Topsoil is acidic due to coniferous needles

Tundra

• Treeless land

• Underneath topsoil is ______________

• Slow decaying of nutrients, poor soil

Discuss with your table partner:

Low precipitation in the Tundra and Taiga

From the graph, notice that the tundra and taiga are two of the biomes with the lowest annual precipitation. Discuss why these biomes might have such low precipitation.

Cold air can hold much less water, so these very cold biomes have much less moisture in the air and very low precipitation.

Adaptations of Organisms for Their Biomes Trees in temperate forests have leaves, while trees

in the taiga have needles. How do these characteristics help in each biome?

Discuss with your table partner:

Plant leaves/needles have opening to let in CO2 and let out excess O2. Water also exits through these openings (transpiration).

Needles have much _________________ than the broad leaves of many deciduous trees. This reduced surface area prevents the loss of excess water vapor in the drier taiga climate.

Marine Biomes Photic zone (Photo= light): upper portion that light

can penetrate. (about 200 m)

Often contains a large amount of plankton (microscopic marine organisms).

Phytoplankton = ______________ plankton Zooplankton = _____________plankton

Aphotic zone: lower portion of the ocean that light can not penetrate

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Estuary: a body of water with a mix of ______________, found in coastal zones partially surrounded by land.

Often highly productive zones.