7 name and explain each of the three types of symbiosis
chapter 5: population ecology
8 define the following terms:
a limiting factor
b carrying capacity
9 explain the difference between immigration and emigration
10 population growth rate (pgr) is births minus deaths. what does it mean if a population’s pgr is equal to zero?
11 list some examples of density - dependent factors. list some examples density - independent factors
chapter 7: humans in the biosphere
12 define the following terms:
a renewable resource
b nonrenewable resource
13 what is sustainable development? list some sustainable development strategies.
14 what is biodiversity? what threatens it?
15 ddt is a chemical that causes biological magnification. what does biological magnification mean?
16 in a food web, does the amount of energy increase or decrease as it goes up? by how much? where does the energy go?
17 how does the introduction of an exotic species impact an environment?

Question

7 name and explain each of the three types of symbiosis
chapter 5: population ecology
8 define the following terms:
  a limiting factor
  b carrying capacity
9 explain the difference between immigration and emigration
10 population growth rate (pgr) is births minus deaths. what does it mean if a population’s pgr is equal to zero?
11 list some examples of density - dependent factors. list some examples density - independent factors
chapter 7: humans in the biosphere
12 define the following terms:
  a renewable resource
  b nonrenewable resource
13 what is sustainable development? list some sustainable development strategies.
14 what is biodiversity? what threatens it?
15 ddt is a chemical that causes biological magnification. what does biological magnification mean?
16 in a food web, does the amount of energy increase or decrease as it goes up? by how much? where does the energy go?
17 how does the introduction of an exotic species impact an environment?

Accepted Answer

Since there are multiple sub - questions, we'll answer them one by one using the Answer - Explanation Format.

### Question 8a: Define Limiting factor
# Brief Explanations:
A limiting factor is an environmental factor (such as food, water, space, or a particular nutrient) that restricts the growth, abundance, or distribution of a population within an ecosystem. If the amount of this factor is insufficient or exceeds a certain tolerance range for the organisms in the population, it will limit how large the population can grow or where it can live.
# Answer:
A limiting factor is an environmental factor that restricts a population's growth, abundance, or distribution in an ecosystem.

### Question 8b: Define Carrying capacity
# Brief Explanations:
Carrying capacity (often denoted as $K$) is the maximum number of individuals of a particular species that an ecosystem can support over a long - term period, considering the available resources (like food, water, shelter) and the ability of the ecosystem to absorb the waste produced by the population. When a population reaches the carrying capacity of its environment, its growth rate will typically stabilize (or may start to decline if resources become over - used).
# Answer:
Carrying capacity ($K$) is the maximum number of a species an ecosystem can support long - term with available resources.

### Question 9: Explain the difference between immigration and emigration
# Brief Explanations:
Immigration refers to the movement of individuals into a particular population or geographic area from another area. For example, birds from a different region flying into a forest to join the local bird population. Emigration, on the other hand, is the movement of individuals out of a population or geographic area to another area. For instance, some fish leaving a lake to go to a larger river system. So the key difference is the direction of the movement of individuals relative to a specific population: immigration is moving in, emigration is moving out.
# Answer:
Immigration: movement of individuals into a population/area. Emigration: movement of individuals out of a population/area.

### Question 10: Population Growth Rate (PGR) is births minus deaths. What does it mean if a population’s PGR is equal to zero?
# Brief Explanations:
The population growth rate formula is $PGR=\text{Births}-\text{Deaths}$ (we can also consider immigration and emigration in a more comprehensive formula, but for this basic case, we focus on births and deaths). If $PGR = 0$, it means that the number of births in the population is equal to the number of deaths. So, the size of the population will remain stable (assuming no significant immigration or emigration). There will be no net increase or net decrease in the number of individuals in the population.
# Answer:
If a population’s PGR (births - deaths) is zero, the number of births equals the number of deaths, and the population size remains stable (assuming no major immigration/emigration).

### Question 11: List some examples of density - dependent factors and density - independent factors
#### Density - dependent factors:
# Brief Explanations:
Density - dependent factors are factors whose effects on a population change with the population's density.
- **Competition for resources**: As the population density increases, organisms compete more intensely for limited resources like food, water, and space. For example, in a forest with a high density of deer, there will be more competition for the available vegetation.
- **Disease**: In a dense population, diseases can spread more easily from one individual to another. For instance, in a crowded chicken coop, a virus can quickly infect many chickens.
- **Predation**: As the prey population density increases, predators may have an easier time finding and catching prey, which can then limit the prey population. For example, if there are a lot of rabbits (high density), foxes (predators) will have more opportunities to hunt them.

#### Density - independent factors:
# Brief Explanations:
Density - independent factors are factors that affect a population regardless of its density.
- **Natural disasters**: Events like earthquakes, floods, or wildfires will impact a population no matter how many individuals are present. A flood can destroy the habitat of a small or large population of frogs in a wetland equally (in terms of the force of the disaster, though the absolute number of affected individuals may differ).
- **Climate change (extreme temperature changes)**: A sudden and extreme drop or rise in temperature can affect a population. For example, a late frost can kill off a crop (and the insects that depend on it) regardless of how dense the crop or insect population was.
- **Human - caused disturbances (e.g., clear - cutting of forests)**: When humans clear - cut a forest, it impacts all the species in that area, whether their populations were dense or not.

# Answer:
- Density - dependent factors examples: Competition for resources, Disease, Predation.
- Density - independent factors examples: Natural disasters (e.g., floods), Extreme temperature changes, Human - caused clear - cutting of forests.

### Question 12a: Define Renewable resource
# Brief Explanations:
A renewable resource is a natural resource that can be replenished or regenerated over a relatively short period of time (on a human - time scale or within the ecosystem's natural cycles). Examples include solar energy (the sun continuously emits energy), wind energy (wind is constantly generated by atmospheric processes), and forest resources (if forests are managed sustainably, trees can be replanted and grow back). These resources are not depleted permanently when used, as long as the rate of use does not exceed the rate of renewal.
# Answer:
A renewable resource is a natural resource that can be replenished/regenerated over a short time (e.g., solar energy, wind, sustainable forestry products).

### Question 12b: Define Non - renewable resource
# Brief Explanations:
A non - renewable resource is a natural resource that is formed over extremely long geological time scales (millions of years) and is present in a finite amount. Once it is used up, it cannot be replaced within a human - relevant time frame. Examples include fossil fuels (coal, oil, natural gas), which are formed from the remains of ancient organisms, and minerals like gold or diamonds, which are formed through geological processes that take a very long time.
# Answer:
A non - renewable resource is a finite natural resource formed over long geological times, not replenished quickly (e.g., fossil fuels, gold).

### Question 13: What is sustainable development? List some sustainable development strategies
#### What is sustainable development?
# Brief Explanations:
Sustainable development is development that meets the needs of the present generation without compromising the ability of future generations to meet their own needs. It involves balancing economic growth, social well - being, and environmental protection. For example, developing a city in a way that uses renewable energy sources, protects green spaces, and provides good living conditions for its residents while ensuring that future generations will also have access to clean air, water, and resources.

#### Sustainable development strategies:
# Brief Explanations:
- **Renewable energy adoption**: Using solar, wind, or hydroelectric power to reduce dependence on non - renewable energy sources and cut down on greenhouse gas emissions. For example, a country installing large - scale solar farms.
- **Sustainable agriculture practices**: Practices like organic farming (which avoids synthetic pesticides and fertilizers), crop rotation (to maintain soil fertility), and agroforestry (combining trees and crops) to ensure long - term food production while protecting the soil and water quality.
- **Efficient water management**: Implementing water - saving technologies in households (like low - flow toilets and showerheads) and in agriculture (like drip irrigation) to ensure that water resources are used efficiently and are available for future generations.
- **Waste reduction and recycling**: Reducing the amount of waste generated (through practices like reducing single - use plastics) and recycling materials (like paper, glass, and metal) to conserve resources and reduce the burden on landfills.

# Answer:
- Sustainable development: Development that meets present needs without compromising future generations' ability to meet theirs (balances economic, social, environmental needs).
- Sustainable development strategies: Renewable energy adoption, sustainable agriculture, efficient water management, waste reduction/recycling.

### Question 14: What is biodiversity? What threatens it?
#### What is biodiversity?
# Brief Explanations:
Biodiversity (biological diversity) refers to the variety of life on Earth at all levels of biological organization. This includes:
- **Genetic diversity**: The variety of genes within a species. For example, different breeds of dogs have different genetic make - ups.
- **Species diversity**: The number and variety of different species in a particular area or on the planet. For example, a rainforest has a high species diversity with many different types of plants, animals, and fungi.
- **Ecosystem diversity**: The variety of different ecosystems (like forests, grasslands, oceans, and wetlands) on Earth.

#### What threatens biodiversity?
# Brief Explanations:
- **Habitat loss**: The destruction, fragmentation, or degradation of habitats. For example, deforestation for agriculture or urban development destroys the habitats of many forest - dwelling species like orangutans.
- **Invasive species**: Non - native species that are introduced to an ecosystem (either intentionally or accidentally). These species can out - compete native species for resources. For example, the introduction of the brown tree snake to Guam has led to the extinction of many native bird species.
- **Climate change**: Changes in temperature, precipitation patterns, and sea levels can disrupt ecosystems. For example, rising sea levels can flood coastal habitats, and changes in temperature can cause species to shift their ranges, which can disrupt food webs.
- **Over - exploitation**: The unsustainable use of natural resources. For example, overfishing of certain fish species (like bluefin tuna) can lead to a sharp decline in their populations, and over - hunting of animals like elephants for their ivory has threatened their survival.
- **Pollution**: Pollution of air, water, and soil. For example, water pollution from industrial waste can kill aquatic organisms and disrupt aquatic ecosystems, and air pollution can harm plants and animals that breathe in polluted air.

# Answer:
- Biodiversity: Variety of life on Earth at genetic, species, and ecosystem levels.
- Threats to biodiversity: Habitat loss, invasive species, climate change, over - exploitation, pollution.

### Question 15: What does biological magnification mean?
# Brief Explanations:
Biological magnification (also known as biomagnification) is the process by which the concentration of a toxic substance (such as a pesticide like DDT, a heavy metal like mercury) increases as it moves up the food chain. For example, a small amount of DDT may be present in water. Phytoplankton (tiny aquatic plants) absorb a small amount of DDT. Then, small zooplankton (animals that eat phytoplankton) eat many phytoplankton, so the DDT concentration in the zooplankton is higher than in the phytoplankton. Small fish eat many zooplankton, so the DDT concentration in the small fish is higher than in the zooplankton. Large fish eat many small fish, and so on. At the top of the food chain (e.g., in birds of prey or humans), the concentration of the toxic substance can be very high, which can cause harm to these top - level consumers.
# Answer:
Biological magnification is the increase in concentration of a toxic substance as it moves up a food chain.

### Question 16: In a food web, does the amount of energy increase or decrease as it goes up? By how much? Where does the energy go?
# Brief Explanations:
- **Energy change with trophic level**: In a food web, the amount of energy decreases as it moves up the trophic levels (from producers to primary consumers, then to secondary consumers, etc.).
- **Energy transfer efficiency**: On average, only about 10% of the energy available at one trophic level is transferred to the next trophic level. This is known as the 10% rule. For example, if a producer (like a plant) has 1000 kcal of energy available, a primary consumer (like a grasshopper that eats the plant) will only get about 100 kcal of that energy, a secondary consumer (like a bird that eats the grasshopper) will get about 10 kcal, and a tertiary consumer (like a hawk that eats the bird) will get about 1 kcal.
- **Where the energy goes**: The majority of the energy (about 90% at each trophic level) is used by the organisms at that level for their life processes. This includes:
    - **Respiration**: Organisms use energy from food to perform cellular respiration, which releases energy for activities like movement, growth, and reproduction, and also releases heat (which is lost to the environment).
    - **Waste production**: Some of the energy is lost in the form of waste (like feces), which is then decomposed by other organisms in the ecosystem.

# Answer:
- Energy decreases as it moves up a food web.
- On average, about 10% of energy is transferred between trophic levels (the 10% rule).
- Energy is used for respiration (releasing heat), waste production, and life processes (movement, growth, reproduction).

### Question 17: How does the introduction of an exotic species impact an environment?
# Brief Explanations:
- **Competition with native species**: Exotic species may out - compete native species for resources such as…

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QUESTION IMAGE

Question

Explanation:

Question 8a: Define Limiting factor

Answer:

Question 8b: Define Carrying capacity