5 -- Part 2: . The Inhabitants of Planet Earth and Their Relationships
The bottom step of a food chain is the producer and the top step is a secondary or tertiary consumer.
In food chains, the arrows depict the transfer of energy through the levels, and in fancier food chains, the relative biomass of each trophic level will often be represented.
There is a simple food chain.
There are different types of fish and different types of algae in the aquatic food chain that we're showing here.
Only 10% of the energy is transferred from one level to the next in a food chain.
The 10% rule is known.
The primary consumers have less energy than the producers, the secondary consumers have less energy than the producers, and the tertiary consumers have less energy than the producers.
An energy pyramid is the amount of energy available at each trophic level.
An energy pyramid is shown for an aquatic food chain.
In this example, the producers start with 100,000 grams of energy, but only 10,000 grams are transferred to the primary consumers.
With each step up the food chain, energy is lost and only a small amount is transferred.
There are models for both numbers and biomass.
tertiary consumers are the first to be affected by environmental problems because they show the decreasing number of organisms at each level.
Other things can flow through food chains, too, including environmental toxins.
Since most toxins cannot be broken down by organisms, the concentration of certain toxins increases at each successive level.
The term bioaccumulation is used to describe the build up of a toxic chemical in a living organisms tissues.
The term biomagnification is used to describe the concentration of the toxin in a food chain.
The terms bioaccumulation and biomagnification are used to describe toxins and heavy metals.
This is how they will be used on the test.
Food chains are an oversimplified way of showing the many feeding relationships that exist in the environment.
The relationships of plants and animals in the real world are more complex than can be depicted in a single food chain.
We use a food web in order to represent feeding relationships in a more realistic way.
Let's talk about the setting for food chains and food webs.
All forms are the result of evolution.
Over time, a population's genetic composition changes.
A tree is used to model evolution.
You won't need to know much about evolution for this exam, but you will need to have a rough idea of how and why it happens.
Without trying to recreate the evolution of all living organisms, we will limit our discussion to a description of how new species are formed.
The process is called speciation.
A species is defined as a group of organisms that are capable of breeding with one another, and incapable of breeding with other species.
Individual organisms that are better adapted for their environment will live and reproduce, ensuring that their genes are part of their population's next generation.
Evolutionary fitness is what Charles Darwin meant.
Natural selection is when a habitat selects certain organisms to live and reproduce and others to die.
Negative characteristics that can be passed down to the next generation are less common in the population because of natural selection.
Natural selection acts upon a whole population, not on a single individual.
Natural selection is one of the mechanisms that evolution uses to change the total genetic makeup of the population.
The term survival of the fittest doesn't refer to the fastest or strongest person.
Those organisms that produce offspring will also produce offspring.
Genetic drift is the other way evolution operates.
Random chance can cause genetic drift, which is the change in the frequencies of alleles due to sampling errors.
In a population of owls, there may be an equal chance of a newly born owlet having long talons or short talons, but due to random breeding, a slightly larger number of long-taloned owlets are born.
This slight variation can develop into a larger trend until most of the owls in that population have long talons.
An earthquake that reduces the size of the population one year could be the reason for the breeding variances.
Small populations are more sensitive to genetic drift than large populations.
Microevolution occurs when a population displays small-scale changes.
Other species may become extinct as a result of natural selection and genetic drift.
All members of a species die when a species cannot adapt quickly to environmental change.
The true end of a species is called biological extinction.
There are no individuals of this species left on the planet.
When there are so few individuals of a species that they can no longer perform their ecological function, it's called ecological extinction.
For example, the groundfish population of the Grand Banks off the Maritimes of Canada is not worth the effort it takes to locate and harvest them.
Let's discuss how species get along.
When a group of organisms of the same species occupy the same geographic area, they form a community.
There is an ecological niche for every species in the community.
The total sum of a species' use of the biotic and abiotic resources in its environment is called a species' niche.
The niche describes where the species lives, what it eats, and all of the other resources it uses.
Habitat is a term you should know about for the exam.
Some species interact with other members of their population in ways that are similar to bears.
There are many reasons for the different levels of sociability.
Two people are competing for resources in the environment.
Interspecific competition is when the two individuals competing are of different species.
Food, air, shelter, sunlight, and various other factors necessary for life are some of the resources that are competed for.
The competitor who is the most fit wins.
The others are eliminated by competition.
The phenomenon of competitive exclusion is when two different species in a region compete and the better adapted one wins.
Gause's principle states that no two species can occupy the same niche at the same time and that the species that is less fit to live in the environment will relocate, die out, or occupy a smaller niche.
When a species occupies a smaller niche than it would in the absence of competition, it is called a realized niche.
The cause of resource partitioning can be avoided with direct competition.
When different species use different parts of the same habitat, they rely on the same resource.
Five warblers can all live in the same pine tree.
They can coexist because each species feeds on different parts of the tree.
It's easy to observe competition between animals and plants, but it's more subtle and takes more time.
If you have a few years to kill, you should spend some time in your backyard watching the trees and plants grow.
Predators are the second important type of interspecies interaction.
Changes in population size are caused by predation when one species feeds on another.
In a year in which there is a lot of rain in some areas, rabbits will be able to reproduce and the number of rabbits in a population will increase dramatically.
coyotes will have a lot of food if the coyote is a predator of the rabbit.
There will be less grass if the following year's rain is below average.
There will be a decline in the population of rabbits and coyotes.
The symbiotic relationship is a third type of relationship.
Symbiotic relationships are not always beneficial for each member.
You should be familiar with all three types of symbiotic relationships on exam day.
This type of relationship exists between sea anemone and clown fish.
The stinging cells of the anemone protect the clown fish, while the fish also eats some of the debris left behind when the anemone feeds.
In commensalistic relationships, one organisms benefits while the other is neither helped nor hurt.
The trees are not affected by the epiphytes growing in them, and the epiphytes benefit by collecting water running down the bark and getting better access to light than they would on the ground.
Parasitis is a relationship in which one species is harmed and the other benefits; for example, the relationship that exists between fleas and dogs.
The biotic balance in a community is maintained by a single species, known as the keystone species.
The keystone is named after the last stone placed in an arch bridge.
keystone species is a species whose extinction would cause the extinction of other forms of life.
fig trees are the keystone species in a tropical forest, and wolves were brought back into the park to control the number of herbivores.
If the keystone species is removed from the system, it will change completely.
Indicator species are used to evaluate the health of an environment.
They can be used as an early warning system to detect dangerous changes to a community because they are more sensitive to biological changes.
The trout are sensitive to pollutants in the water.
The disappearance of trout from a particular area is a sign that the area is becoming polluted.
Indigenous species are those that are native to the area or environment.
New species are being introduced into the system by chance or with intent.
Many introduced species are happy in their new environment and compete successfully with the indigenous species.
The grey squirrels were introduced to England in 1876.
There are fewer than 30,000 red squirrel alive in England today, and the grey squirrel competed with them.
An example of the harm that introduced species can do is when a fungus was accidentally introduced into the eastern United States in 1904.
The chestnut trees were killed by a disease caused by this fungus.
Some people don't like to use the term "invasive species" because they feel that it's derogatory, but it is often used to describe introduced species.
The zebra mussels were introduced into the Great Lakes when ships dumped water into the lakes in order to control the problem of erosion.
Communities are constantly changing.
Plants and animals are constantly evolving and dying out.
Ecological succession can be defined as the predictable changes that take place in a geographic area.
The area below a retreating glacier is called primary succession if ecological succession begins there.
When an existing community has been cleared by a fire, tornado, or human impact, the soil has been left intact, which is called secondary succession.
The organisms in the first stages of succession are referred to as pioneer species because of their wide range of environmental tolerance.
Over time, these pioneers adapt to the conditions of the habitat.
This could result in the creation of new species.
The environmental changes that will allow the next stage to take over facilitate the communities in each stage.
The climax community is the final stage of succession in which there is a balance between the abiotic and biotic components.
The community of lichens is where the first stage of the job usually begins.
Lichens are hardy.
They can invade an area, land on bare rocks and turn them into soil over time.
Lichens are pioneer organisms.
Other organisms can come in once the area has been made more hospitable by the lichens.
With the introduction of each new plant species comes an array of different animal species that exploit it, so remember that the stages are classified by the major new plant group.
We're almost done with this chapter, but you need to know a few more terms and concepts before you can move on to the population chapter.
The material will be asked about on the test.
When the size of an organisms natural habitat is reduced, this is called habitat fragmentation.
Habitat fragmenting can be very damaging.
Ecotones are wide and overlaps, and they are abut each other.
The edge effect is when there is greater species diversity and biological density than in the center of ecological communities.
If the boundaries of a habitat are changed, a new edge is created, damaging both the edge and interior habitats.
The theory of island biogeography was first developed to address species diversity on actual islands, but has since been extended to apply to areas that are surrounded by populated areas.
The number of species found on an undisturbed island is determined by two factors: immigration and extinction.
Don't forget to use the techniques you learned in Part III if you want to move on to the next chapter.
You need to know how to use these words in your essays.
You can download a PDF of Chapter 5 Drill.
Four suggested answers or completions are followed by each of the questions or incomplete statements.
Pick the one that is the best.
Chapter 13 has answers and explanations.
Students from a local high school studied a pond.
They determined the average concentration of compound "X" in each sample after taking samples of small fish, a fish-eating hawk, pond water, and zooplankton.
Their data is summarized in the table below.
Take the concentrations of compound "X" for each part of the chain.
The substance might have a negative effect on humans.
There are five major biogeochemical cycles.
All food chains move energy through the various trophic levels that make up the system.
The main parts of the planet are the forest, tropical rainforest, grassland, taiga, tundra, chaparral, and deserts.
The aquatic zones are categorized by the salinity, while the Terrestrial biomes are defined by their average rainfall and annual temperature.
Each zone has a specific range of tolerance for certain species.
Ecotones are the regions where the different biomes meet.
The result of speciation and natural selection is the diversity of the Earth's flora and fauna.
niches can become available and new species can evolve to use them.
Populations of species with unique niches can be thought of as part of the organization of living things.