Grade 7 - Interactions and Ecosystems

Section 1: Interactions Within Ecosystems

Ecology is the study of the relationship between living organisms and their environment. An ecologist is someone who studies those relationships. Living things are always interacting with each other and with the non-living things in their environment. Ecologists also explore the relationships between humans, animals, and the environment.

Living things need:

Water: Humans are almost two-thirds water! Living things need water for various biological processes and cannot function properly and will eventually die without water.
Food - Animals eat food, while plants make it. Food gives living things energy. Food also provides nutrients such as fat, protein, and carbohydrates, which help living things to grow, repair, and reproduce themselves.
Suitable habitat: Many creatures, such as the mountain goat, live in a particular sort of environment without any type of shelter. Others, including humans, beavers, and wasps, build protective shelters.
Air: All living things exchange gases. Plants, for instance, use carbon dioxide to make food and “breathe” off oxygen. Other living things, including fungi and bacteria, need oxygen too.

Living things are adapted, so they 'fit' into their environment, to ensure survival. An adaptation is a characteristic that is inherited or learned during the organism's lifetime, to help an organism survive and reproduce in its environment.

Ecosystems

An ecosystem is a biological system characterised by interactions between living and non-living things in a particular environment. An ecosystem is a place where these interactions occur. The ecosystem of a rotting log is formed by the interactions between the organisms living in and on the log and the soil, temperature, and other non-living features around the log. A forest is also an ecosystem. All of the living things, such as trees and animals, and all of the non-living things, such as the sunlight and the air, are interacting. All organisms and parts within this place are interacting all the time and adjustments must occur if the organism is to survive. Ecosystems vary in size and complexity. In order to study an entire ecosystem, scientists often study only a small aspect of an ecosystem and then work with other scientists to piece together the overall picture of how the ecosystem functions.

Interactions in Ecosystems

Symbiosis describes the interaction between two species living closely together in a relationship that lasts over time.
There are three types of symbiosis:

Mutualism: Mutualism occurs when there is a relationship between two different organisms, in which each partner benefits from the relationship. Examples include: herbivores and plants.
Parasitism: Parasitism occurs when there is a relationship between two different organisms, in which one partner benefits from the relationship, while the other partner is harmed. Typically, the partner that benefits (the parasite), lives on or in the other organism (the host) and feeds on it. Examples of parasites include: worms in the gut, mosquitoes, ticks etc.
Commensalism: Commensalism occurs when there is a relationship between two different organisms, in which one partner benefits from the relationship, while the other neither benefits, nor is harmed. For example an orchid plant will attach itself high up a tree trunk to have a safe, sheltered place to grow and receive water dripping down the tree trunk. The tree trunk which provides the habitat for the orchid seems to neither be harmed nor benefit from the relationship.

Symbiotic relationships are only a few ways that organisms interact with one another within an ecosystem. Other interactions may involve the physical changing of the ecosystem by the organisms living in it and interacting with parts of it. Like when a family of beavers make a dam, the stream below the dam dries up, killing the water organisms that need the water to survive. Above the dam, a pond changes the habitat and limits the kinds of organisms that can survive there. For every action in an ecosystem there is a resulting effect and reaction which will change the make-up of the ecosystem in some way.

Section 2: Human Impacts in Ecosystems

Human activity such as energy generation, agriculture, urbanization can impact the environment in a positive or negative way.

Natural Resources are the materials and products that are found in nature, that people use to meet their basic needs. The impact that people have on the use of resources can be very small, or can be huge, and can lead to positive or negative consequences. The needs of all living things now have to be met with the available natural resources. How we are able to satisfy these needs with minimal conflict will determine how resourceful we can be.

People and Nature - A Changing Relationship

Several years ago, the environment would have looked significantly different from how it looks now. The ways people interact with the environment has changed over time. Machines and advanced technologies have caused a higher impact than in the past. All of the needs people had in the past were satisfied by the natural resources they were able to find in the environment around them. Nowadays, resources are transported throughout the world, as the demand gets higher. Lifestyle changes over time have increased the pressure on different environments and the ecosystems we live in.

Human Needs and Wants

Needs are basic to survival, whereas, 'wants' are things that just make survival more comfortable or enjoyable. Each time a need or a want is satisfied, natural resources or energy are used up. This impacts the environment we live in. Transporting food from all around the world, just so we can have the luxury of choice impacts other regions as well, because those regions had to clear land, use fuel (energy) and through the industrial processes caused pollutants to enter the air. When our 'want' demands conflict with the health of our ecosystems, we need to begin making some more responsible choices. The needs of wildlife can be negatively impacted by the wants of people. When this happens we need to decide whether our want is more important than their need. But its not a simple solution. For example, Canada cannot produce pineapples, coconuts, avocadoes, oranges, lemons and many crops and fruits, yet the people would love to have access to these foods to meet their needs for a nutritious diet. Some impacts are even more complicated to measure. Many farmers used to burn their land after harvest and allow fresh vegetation to grow during the rain season, a practice that was deemed to be harmful to the environment, but as less farmers burn their fields leaving dry stubble on the growund, there has been an increase in wild fires, which are less controlled and often burn homes. There has also been reduced regrowth of vegetation in spring because of the accummulation of old dry but not rotten vegetation. Commercial agriculture is aimed to increase production of specific crops and provide food for the ever increasing human population, while several practices implemented by commercial agriculture producers (such as excessive fertilizers, herbicides etc) may be harmful to the environment including aquatic habitats. How can decision makers balance the need to provide food and the need to conserve the environment at the same time.

Knowing what effects you are having on the environment (or will likely have) will help you make decisions.

Section 3: Environmental Choices

We depend on the environment and we are part of the environment. We utilise resources from the environment for our survival. Sustainability means that the resources we use from the environment can be replaced as quickly as we consume them. Are we putting back what we take out, or, are we using up all the resources before they can be replaced? To calculate our ecological footprint, we need to determine the total area of land that we use and water needed to supply all of the energy and materials that we use, as well as absorb all of the waste that we produce. The materials include food, water, supplies to build shelter and raw materials needed to produce the manufactured products we use. Energy includes electricity, natural gas, as well as all the energy needed to produce, and transport all of the manufactured products we use. Of course this is a complicated calculation.

The ecological footprint of average person in industrialized countries is very large, because they are using many more resources and creating much more waste than is sustainable.

Some ways to reduce our ecological footprint include:

Be aware of the products we consume in a typical day
Reduce the energy we use
Reduce the number of products we buy
Reduce the amount of garbage you produce

The 3 R's of sustainability

Reduce - Reduce production and use -
Reducing the amount of raw material needed for production, and the amount of product we use in general.

Reuse -
Reuse resources and products like containers, shopping bags, storage containers etc. Appropriate processes such as washing and sterilization maybe required. Items may be reused for a purpose different from the original, intended use.

Recycle - Some items can be recycled to make other new items. These include cardboard, milk containers, juice bottles, soda cans etc.

Section 4: How Organisms Interact

Living organisms make up the biotic components of the ecosystem, while non-living things make up the abiotic parts of the same ecosystem. Biotic community comprises of plants, animals and microbes. Abiotic factors include soil, land, climate/weather etc.

All of the organisms within an ecosystem have different roles. These roles are called niches. Organisms can have more than one niche and knowing the niches of an organism can help to explain why they act and interact the way they do. To determine an organism's niche, you need to identify what it eats, where it lives and how it interacts with the other organisms in the same ecosystem.

Niches include:

Producers - produce food energy for themselves and others
Consumers - consume the food made by the producers
Herbivores - eat producers (plant eating niche)
Carnivores - eat other consumers (meat eating niche)
Predators eat prey
Omnivores - eat both producers and consumers

Food Chains

A food chain is a model that shows how energy stored in food passes from one organism to another.

Energy flow is the movement of energy, starting with the sun, and passing from one organism to another. As energy flows from one organism to another a food chain is established. Food chains usually involve more than three organisms.

Food Webs

A food web is a combination of many different food chains, showing the interrelationships between and many different producers and consumers in an ecosystem.

Food Pyramid

A Food Pyramid is a model representing the numbers of organisms consumed at each successive level of the pyramid. The size of the level indicates the number of organisms at that level. There are always more animals being eaten than are eating. To find out how much energy is being transferred from one level of the pyramid to the other, Biomass needs to be calculated. Biomass is the total of all the organisms in the ecosystem. As you move up the pyramid, there is less biomass. The most biomass is found at the base, where the producers are.

Decomposers and Scavengers

Scavengers are organisms that feed on dead or decaying plant or animal matter.
Decomposers are different from scavengers because they do not actually eat dead material. They grow on or in the dead or waste matter, absorbing the nutrients directly into their cells, which are then recycled back into the environment.

Section 4: Cycles in the Environment

When organisms breathe, the gases are recycled in the air and used by other organisms. When organisms die, their nutrients are recycled back into the environment and used as well. Water is also recycled in the environment as shown in the water cycle below.

Pollution

Pollution occurs when a substance is added to the environment at such a fast rate that it cannot be broken down, stored or recycled in the air, land, or water in a non-damaging form. Pollutants are substances that cause pollution. Sulfur and Nitrogen at higher than normal levels in the air, mix with water to produce acidic precipitation known as acid rain. Burning of Fossil fuels puts higher than normal levels of CO₂ into the atmosphere and the ozone layer, which protects us from radiations from the sun. This potentially results in global warming.

Bioaccummulation and Biomagnification

Bioaccumulation is the process in which a substance builds up inside a living organism from the surrounding air or water, or through the consumption of organisms that already have the substance that is being accumulated. It will vary for different species and will depend on sources of contamination, as well as water quality and temperature. It provides increasing levels harmful to species higher up the food chain, because of "biomagnification", where substances like mercury will increase in concentration as you go up the food chain.

Section 5: Succession and Change in Ecosystems

Succession is the gradual process by which some species within an ecosystem replaces other species.

Primary succession is the gradual growth of organisms in an area that was previously bare ? like a rocky slope. Organisms to first appear are those that can cling to the rock and grow, such as mosses and lichens. These organisms break down the rock and died. Other organisms use the nutrients to begin to grow. Examples of areas in which a community has never lived before would be:

New lava or rock from a volcano that makes a new island or a new landscape
A sand bar that arises from shifting sands in the ocean
The exposure of igneous rock surfaces by a land slide
A meteor makes a depression that fills with rainwater or fresh water from underground streams.

Secondary Succession: The gradual growth of organisms in an area after a disturbance, such as a fire, or when a large tree falls.

Ecosystem Changes Caused by Human Activity

Humans affect the environments around them in many ways, including activities and technologies such as: forestry, industrial processes, transportation, urban development, construction and farming. When an ecosystem is changed by human activity, there can be unexpected consequences.
Some species adapt better than others. For example, some bird species, such as cowbirds, will adapt to farmland easily. Other species, such as coyotes, have been able to adapt to the spread of urban areas, whereas other animals, such as the wolf have not

Pest Control

Pests that can affect human health and crops are a major problem. Besides controlling the pest population a pesticide can also damage other organisms that are not targeted. This occurs with a pesticide that is designed to kill lygus bugs (who damage canola crops). The pesticide will also kill bees. If the pesticide kills the pest predators, then the pest population may actually increase.

Biological Control

Using their own natural predators is another way to control pests. This method is known as biological control. Biological control can however cause other problems. The species that is introduced may have no natural predators and will overtake the area (using up the food supply) so that other organisms cannot survive. Introducing a species not natural to a particular area can cause more problems than what it solves.

For example, zebra mussels were introduced into the Great Lakes and have now become a major problem.

Species In Danger

Many species all over the world are in danger of extinction. If a species becomes extinct, it can no longer be found anywhere in the world. Sometimes the organism is only lost in a large region. If this occurs, the species is extirpated. If a particular species is in danger of becoming extinct, or extirpated, it is placed on the endangered species list. There are special protection programs and laws made to protect endangered species.

Section 6: Environmental Monitoring

Ecosystem monitoring (also called - environmental monitoring) is a way to check the condition - health - of an ecosystem by comparing results of investigations done at different times. Monitoring helps scientists understand impacts of disturbances and changes - sudden and gradual - in order to try to reverse or reduce the impact. Biotic and abiotic factors are monitored.

Environmental monitoring usually begins after a disturbance has taken place. It can also begin before a disturbance occurs. A key part of the monitoring program is to provide the evidence on which environmental decisions can be made to maintain the balance between human needs and the needs of other organisms in the environment. Continuous monitoring gives us the scientific data we need to make informed decisions about how we affect the environment over time.

Monitoring programs may be qualitative, semi-quantitative, or quantitative. Monitoring involves the use of indicators, indicator species or indicator communities. The presence or absence of the indicator or of an indicator species or indicator community reflects environmental conditions.

Ecosystem monitoring types

Physical, uses satellites to track changes in the landscape over time.
Chemical, assesses the quality of air, soil and water
Biological, tracks the changes in organisms or populations of organisms
Environmental tracks changes in climate, temperature and weather patterns.

Baseline Data is collected to give scientists a starting point to compare changes in the environment. Scientists to monitor change use permanent plots, or study areas. The report that provides the data that has been collected - identifying how a certain activity will affect the environment - is called an Environmental Impact Assessment.

Quadrant Sampling is a technique used to study a large are. The quadrant is selected and the species is counted in the quadrant. The number of quadrants in the area provides the multiplier to estimate the population of the species in the area.