5 -- Part 1: . The Inhabitants of Planet Earth and Their Relationships
In the new course and exam description, there are topics in the "The Living World: Ecosystems" unit.
In your biology class, you probably learned that the non living components of Earth are called abiotic components.
We studied the atmosphere in the last chapter.
We'll talk about the biotic components of Earth in this chapter.
We will discuss elements that bridge the gap between living and non living and how they cycle through the environment.
We'll discuss what types of ecosystems exist and how they're structured.
We'll continue our review by discussing how energy flows through the system, and we'll end the chapter with a review of how the system changes.
In your biology class, you may have learned that the environment is made up of many different types of biogeochemical cycles.
You will need to know a bit about these cycles for the exam, so we'll go through each of them here.
Living organisms, geologic formations, and chemical substances are all involved in the natural cycles.
It's important to understand both the destinations of the compounds and how they move towards them when describing their movement.
Water moves from the atmosphere to the surface through precipitation, either in the form of snow or rain.
You need to know that water moves from the atmosphere to the soil to pass the AP Environmental Science Exam.
You need to know how it gets there.
Let's talk about a few of the things that all of these cycles have in common.
In the water cycle, the ocean is an example of a "reservoir", which is a place where a large quantity of a substance sits for a long period of time.
An exchange pool is the opposite of a reservoir and is a site where a nutrient sits for a short period of time.
Residency time is the amount of time a person spends in an exchange pool.
Living organisms can also serve as exchange pools, and we'll look into this later.
The heat energy from the mantle and core of the Earth is what drives the biogeochemical cycles in the biosphere.
The movements of nutrients in all of these cycles can be accomplished through either wind or living organisms.
The Law of Conservation of Matter states that matter can't be created or destroyed, but that it can be rendered unavailable for cycling through certain processes, for example, in some cycles.
You should know that trace elements such as zinc, copper, and iron are necessary in small amounts for living organisms, even though we won't get into a discussion of trace elements here.
There's still much to learn about trace elements and their biogeochemical cycles.
There are certain trace elements required by living things that cycle, along with the major elements, through the biosphere, for this exam.
The water cycle is perhaps the best-known biogeochemical cycle.
When water condenses from a gaseous state to form a liquid or solid, it becomes dense enough to fall to the Earth because of the pull of gravity.
This process is called precipitation.
When precipitation falls onto the Earth, it can either be deposited into a drainage system or trickle through the soil and rock until it reaches the water table.
Lakes and oceans hold water.
Blocks of snow or ice can be found on the surface of Earth in certain cold regions.
There is water in living systems.
Plants consume water and carbon dioxide in the process of photosynthesis, in which they produce carbohydrates and oxygen.
All living organisms are made up of water.
Water is returned to the atmosphere from both Earth's surface and living organisms.
Water vapor and gases are released by animals.
The vast number of lakes and oceans on Earth is one of the major contributors to atmospheric water.
Large amounts of water evaporate from their surfaces.
The following graphic shows all of the forms that water takes in the environment.
Cloud formation is caused by condensation when water becomes liquid or solid.
Let's talk about carbon.
Living things act as exchange pools for carbon.
When plants are eaten by animals, the carbon locked in the plant is transferred to other organisms in the food chain.
CO 2 is released back into the atmosphere when plants and animals die due to the actions ofbacteria and fungi in the soil.
When the bodies of once-living organisms are buried deep and subjected to extreme heat and pressure, this organic matter eventually becomes oil, coal, and gas.
Carbon is released into the atmosphere when fossil fuels are burned or combusted.
Volcanic action releases carbon into the atmosphere.
The world's oceans are the first of the three major sources of carbon.
Earth's rocks are the second large source of CO 2.
The carbonate rocks contain carbon in the form of calcium carbonate.
Fossil fuels have a huge amount of carbon.
The atmosphere on Earth is made up of 78 percent nitrogen and 21 percent oxygen.
Nitrogen is abundant in the atmosphere.
It might not seem like living organisms would find it hard to get the nitrogen they need in order to live.
Most organisms can't use atmospheric N 2 directly.
To keep this cycle straight, let's look at it in steps.
Nitrogen must be present in the form of ammonia or nitrates in order to be used by most living organisms.
Nitrogen can be fixed by atmospheric effects such as lightning storms, but most nitrogen fixation is the result of the actions of certain soilbacteria.
Nitrogen can be made biologically available through the process of fixing.
Rhizobium is one of the important soilbacteria.
These nitrogen-fixingbacteria are often associated with the roots of the plant.
In the future, we may be able to insert the genes for nitrogen fixation into crop plants, such as corn, and reduce the amount of fertilization that is used.
In this process, soilbacteria convert ammonia (NH 3 ) or ammonium (NH 4 + ) into nitrites and then to one of the forms that can be used by plants.
Plants absorb ammonia, NH 3, and NO 3 through their roots.
Heterotrophs, organisms that receive energy by consuming other organisms, then get nitrogen when they consume plants' nucleic acids.
Dead organisms and other waste can be converted to ammonia by decomposingbacteria, which can be used by plants or released into the atmosphere.
In denitrification, specializedbacteria convert ammonia back into nitrates and nitrites, and then into nitrogen gas and nitrous oxide.
The gases rise to the atmosphere.
The simplest biogeochemical cycle is the phosphorus cycle because it doesn't exist in the atmosphere outside of dust particles.
It's necessary for living organisms because it's a major component of nucleic acids.
One thing to remember about the phosphorus cycle is that it is more local than other biological compounds.
Most of the time, phosphorus is found in soil, rock, and sediments; it's released from these rock forms through the process of chemical weathering.
Plants can absorb the form ofphosphate (PO 4 3- ) that is released from the soil.
Symbiotic relationships between plants and fungi are called mycrrohizae.
In these relationships, mychorrhizal fungi colonize the root system of a host plant, which increases the water and nutrient absorption capabilities of the plant.
Plants that have little phosphorus are not able to grow because it is a limiting factor for the population's growth.
Rocks on the ocean floor can eventually be incorporated with thephosphates that enter the water table.
Rocks from the seafloor may rise up so that their components reenter the terrestrial cycle.
Take a look at the diagram.
Humans have affected the cycle by mining.
Eutrophication can be caused by the fertilizers that are placed on the fields.
Eutrophication occurs when a body of water gets too much water.
The overgrowth of algae can deplete the water of oxygen.
The chemistry is almost done.
We need to discuss sulfur before we discuss the biosphere.
The sulfur cycle is the last biogeochemical cycle.
Plants and animals need sulfur in their diet because it is one of the components that make up vitamins and minerals.
When sulfur is dissolved in water, plants can take it up through their roots.
Animals get sulfur by consuming plants.
Some sulfur can be found in the atmosphere, even though most of the Earth's sulfur is tied up in rocks and salts.
The natural ways that sulfur enters the atmosphere are through volcanic eruptions.
Industrial processes produce sulfur dioxide and hydrogen sulfide when sulfur enters the atmosphere.
In Chapter 9 we'll talk about sulfur and how it contributes to air pollution.
It's time to discuss the biotic components of Earth.
Let's look at how energy moves through the system.
We can place them in broad categories because of the differences in their abiotic and biotic components.
The two largest categories are the ones that are based on land and the ones that are in the water.
Freshwater and saltwater are classified into separate categories by the amount of water in their bodies of water.
Climate, geology, soils, topography, hydrology, and vegetation are some of the factors that determine land environments.
The table on the following page seems to show a lot of different biomes, but they do not have distinct boundaries.
Ecotones are areas where two ecosystems meet.
Ecozones are smaller regions within the ecosystems that share similar physical features and are an important term for the exam.
The types of organisms that are capable of living in a particular area are determined by the characteristics of that area.
The availability of water, the temperature, and how much sunlight the region gets are some of the characteristics.
The Law of Tolerance is an important law for this test.
The degree to which living organisms are able to tolerate changes in their environment is known as the Law of Tolerance.
Living organisms exhibit a range of tolerance, and even individuals within a population can tolerate changes to their environment differently.
The basis for natural selection is this concept.
The Law of the Minimum states that living organisms will continue to live, consuming available materials until the supply of these materials is exhausted.
The number and variety of organisms found within a specified geographic region is referred to as the biodiversity term.
Variation among living organisms, including the variability within and between species, is also referred to.
If we don't specify the aspect of biodiversity that we're describing, the term is too vague to be understood.
In general, it's a good thing.
The abiotic components are the non living components of the environment.
The atmosphere, hydroosphere, and lithoosphere are included.
The study of the living, biotic components of Earth is about to begin.
All of the living things on Earth are part of the biosphere.
Living things can be classified by how they get food.
You might recall that plants and some cyanobacteria can make their own food, and that some animals can eat plants.
Some animals eat both plants and animals, and some animals only eat other animals.
There are two fancy terms that are used to describe these broad categories of organisms: autotrophs are organisms that can produce their own organic compounds from chemicals, while Heterotrophs are organisms that can consume other organisms or products created by other organisms.
Producers are organisms that can convert energy into food.
Plants and algae are included in the group of producers.
The reaction of photosynthesis is shown.
While most producers make food through photosynthesis, a few autotrophs make food from chemicals in the air.
Chemosynthesis is only carried out by a few specializedbacteria, called chemotrophs, which are found in the ocean.
The unbalanced reaction is shown.
Let's talk about a few environmental science terms that you'll need to know for the exam.
The amount of energy plants pass on to the community of herbivores is called the Net Primary Productivity.
It is calculated by taking the Gross Primary Productivity, which is the amount of sugar that the plants produce, and subtracting from it the amount of energy the plants need for growth, maintenance, repair, and reproduction.
kilo calories per square meter per year is the measurement.
The rate at which the producers are converting solar energy to chemical energy is known as the Gross Primary Productivity.
Net productivity is a limiting factor for the number of consumers.
A population's growth is controlled by a limiting factor.
It can be a lot of things, including space, available food, water, and the net productivity of an environment.
Consumers need to get food energy from secondary sources, for example, by eating plant or animal matter.
The primary consumers include the herbivores, who consume only producers.
A secondary consumer is an organisms that consumes a primary consumer.
A tertiary consumer is an organisms that consumes a secondary consumer.
The organisms derive energy from consuming dead animals or fallen leaves.
They include arthropods.
Decomposers are organisms that consume dead plants and animals.
bacteria and fungi are included in saprotrophs, which are decomposers that break down dead organisms.
The organisms may occupy multiple levels of the food chain.
You are a primary consumer if you eat tomatoes and lettuce, and a secondary consumer if you eat beef.
Let's talk about how energy flows through different types of organisms.
The Sun to producers, to primary consumers, to secondary consumers, to tertiary consumers are all in one direction.
Each feeding level is referred to as a trophic level.
The amount of energy available to the next level decreases with each successive trophic level.
Most of the energy from one trophic level is lost as heat, and some is used for metabolism and anabolism.
Food chains rarely have more than four trophic levels.