Home » Biology » Ecology



Ecological succession

What is Ecological Succession? Texas Gateway

Succession CK-12

Henry Chandler Cowles, one of the founders of the field

Great graphic


Content objective:

What are we learning and why are we learning this? Content, procedures, or skills.

Vocabulary objective

Tier II: High frequency words used across content areas. Key to understanding directions & relationships, and for making inferences.

Tier III: Low frequency, domain specific terms.

Building on what we already know

Make connections to prior knowledge. This is where we build from.


What Is Ecology?

The study of the relationships between living organisms and their physical environment.

Ecology provides information about the benefits of ecosystems, and how we can use Earth’s resources in ways that leave the environment healthy for future generations.

Ecologists study these relationships among organisms and habitats of many different sizes, ranging from the study of microscopic bacteria growing in a fish tank, to the complex interactions between the thousands of plant, animal, and other communities found in a desert.

An ecosystem includes:

all of the living organisms in an area, along with the non-living parts of the environment (weather, ground/rocks, sunlight, soil, atmosphere, rain).

Ecosystems depend on the energy that moves in and out of that system.
You could have an entire ecosystem underneath a big rock.

There is an overall ecosystem of the entire planet the biosphere.

An ecosystem can be as small as a puddle or as large as the Pacific Ocean.

New Hampshire ecosystem Pawtuckaway State Park

Energy flows through ecosystems in one direction
From the Sun, through photosynthetic organisms (including green plants and algae),
to herbivores, to carnivores and then to decomposers.

Energy flow through an ecosystem

{ image from http://karimedalla.wordpress.com/2013/05/01/5-1b-energy-in-ecosystems/ }

Each rectangle in an energy pyramid shows the amount of energy per square meter of area.

Each rectangle is always smaller the level below it.

Why? There is a loss of energy as we move from one “trophic level” to the next. Where is this energy lost to?

* Some organisms die, and rot, without being eaten

* As the organism, it constantly takes in food & energy every day – and then loses most of this energy as body heat – “waste heat.”

* Even when an organism is eaten, not all parts of it are edible. The inedible parts contain energy that is “lost” to the predator.

Ecosystem energy pyramid

Ecosystem energy pyramid

The Carbon Cycle
{ http://eschooltoday.com/ecosystems/the-carbon-cycle.html }

The carbon cycle is very important to all ecosystems, and ultimately life on earth. The carbon cycle is critical to the food chain.

Living tissue contain carbon, in proteins, fats and carbohydrates. The carbon in these (living or dead) tissues is recycled in various processes.

Human activities like heating homes and cars burning fuels (combustion) give off carbon into the atmosphere.
During cellular respiration, animals also introduce carbon into the atmosphere in the form of CO2 (carbon dioxide.)

CO2 in the atmosphere is absorbed by green plants (producers) to make food in photosynthesis.

When animals feed on green plants, they pass on carbon compounds to other animals in the upper levels of their food chains.

Animals give off CO2 into the atmosphere during respiration.

CO2 is also given off when plants and animals die: Decomposers (bacteria and fungi) break down dead plants and animals (decomposition) and release the carbon compounds stored in them.

Very often, energy trapped in the dead materials becomes fossil fuels which is used as combustion again at a later time.



Human influences on some ecosystem processes

Some Ways Humans Adversely Influence Ecosystems

The nitrogen cycle
{ http://eschooltoday.com/ecosystems/the-nitrogen-cycle.html }

Nitrogen makes up 78% of our atmosphere. It is in the form of a nitrogen molecule, N2 (two N atoms bonded together.)

Plants can not use N2 directly from the air. N2 is unreactive.

N2 gas therefore needs to be converted into nitrate compound in the soil. This is done by nitrogen-fixing bacteria in soil, or on plant root nodules. N2 can also be fixed in the soil by lightning.

Consider the diagram below:

1. Nitrogen is introduced to the soil by precipitation (rain, lightning).

2. Nitrates don’t only come from Nitrogen in the air. They can also be obtained by the conversion of ammonia, commonly used in fertilizers by nitrifying bacteria in the soil. Some root nodules can also convert nitrogen in the soil into nitrates.

3. Plants build up proteins using nitrates absorbed from the soil.

4. When animals like cows, eat these plants, they in turn use it to build animal protein.

5-6. When these animals (cows) defecate, urinate or die, the urea, excreta or carcass are broken down by decomposers. The nitrogen is re-introduced into the soil in the form of ammonia.

7. Nitrates in the soil can also be broken down by denitrifying bacteria (in specific conditions) and sent into the air as nitrogen. This process can help make the soil infertile, because it will lack the nitrates needed for plant use.

Once nitrogen gets back into the air, the cycle continues.


Ecology Sample questions

Feb 2016 MCAS: In the past, coyotes lived throughout the western prairies and central Rocky Mountains in North America. Over time, the coyotes’ range has expanded. Humans have tried trapping and hunting coyotes to decrease their numbers. However, biologists currently estimate the number of coyotes to be at an all-time high.  Which of the following statements best explains why the number of coyotes continues to increase despite increases in death rates due to hunting and trapping?

A. Coyote lifespan is increasing, so only the oldest coyotes encounter hunters or trappers.
B. Coyote birth rates remain high, so more coyotes are added to the population than are removed.
C. Coyotes are migrating more often, so male coyotes have more fights over territories.
D. Coyotes have to compete with more species, so the coyote emigration rate has increased.


Feb 2016 MCAS.  Here are the ecological roles of several organisms in a rainforest ecosystem.

fig tree           – producer
jaguar            – secondary consumer
mango tree –  producer
monkey        – primary consumer
toucan bird – primary consumer

a. In your Student Answer Booklet, draw a food web that includes all the organisms listed here. . Make sure the arrows represent the correct direction of energy flow.

Decomposers, such as bacteria, are not listed here:

b. Describe the role of decomposers in the rainforest ecosystem.

c. Describe what would most likely happen to producer populations and consumer populations if all decomposers in an ecosystem were removed. Explain your answer for each type of population.

Learning Standards

Massachusetts Curriculum Frameworks: Biology

HS-LS2-1. Analyze data sets to support explanations that biotic and abiotic factors affect ecosystem carrying capacity.
Clarification Statements:
• Examples of biotic factors could include relationships among individuals (e.g., feeding relationships, symbioses, competition) and disease.
• Examples of abiotic factors could include climate and weather conditions, natural disasters, and availability of resources.
• Example data sets can be derived from simulations or historical data.

HS-LS2-7. Analyze direct and indirect effects of human activities on biodiversity and ecosystem health, specifically habitat fragmentation, introduction of non-native or invasive species, overharvesting, pollution, and climate change. Evaluate and refine a solution for reducing the impacts of human activities on biodiversity and ecosystem health.

Disciplinary Core Idea Progression Matrix

LS1.C Organization for matter and energy flow in organisms

Grades 6-8: Matter cycles between living and nonliving parts of an ecosystem. Plants
use the energy from light to make sugars through photosynthesis. Within individual organisms, food is broken down through cellular respiration, which rearranges
molecules and releases energy.

LS2.B Cycles of matter and energy transfer in ecosystems

Grades 9-10: Photosynthesis captures energy in sunlight and stores it in chemical bonds of matter. Most organisms rely on cellular respiration to release energy in these bonds to power life processes. About 90% of available energy is lost from one trophic level to the next, resulting in fewer organisms at higher levels. At each link in an ecosystem, elements are combined in different ways and matter and energy are conserved. Photosynthesis, cellular respiration and decomposition are key components of the global carbon cycle

%d bloggers like this: