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 (like food, space, or water) that restricts the growth, abundance, or distribution of a population. It acts as a constraint; if its availability changes, the population size or growth rate is affected. For example, in a pond with a limited amount of dissolved oxygen, the number of fish (the population) that the pond can support is limited by the oxygen availability.
# Answer:
A limiting factor is an environmental factor (e.g., food, space, water) that restricts a population's growth, abundance, or distribution.

### 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 environment can sustainably support over a long period of time. It is determined by the availability of limiting factors such as resources (food, water, shelter) and the ability of the environment to absorb waste. For instance, a forest has a carrying capacity for deer based on the available vegetation for food and the space for shelter.
# Answer:
Carrying capacity ($K$) is the maximum number of a species an environment can sustainably support long - term, determined by limiting factors (e.g., resources, waste absorption).

### Question 9: Explain the difference between immigration and emigration
# Brief Explanations:
Immigration refers to the movement of individuals into a population from another area. For example, birds from a different region flying into a forest to join the local bird population. Emigration is the movement of individuals out of a population to another area. For example, some young mammals leaving their birth group to find a new territory. The key difference is the direction of movement: immigration is into a population, emigration is out of a population.
# Answer:
- Immigration: Movement of individuals into a population (e.g., birds entering a forest population).
- Emigration: Movement of individuals out of a population (e.g., young mammals leaving their birth group).
Difference: Direction of movement (into vs. out of a population).

### 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 formula for population growth rate (PGR) is $PGR = Births - Deaths$. If $PGR = 0$, it means that the number of births in the population is equal to the number of deaths. So, the population size will remain stable (neither increasing nor decreasing) from the perspective of birth and death rates (though immigration and emigration can still affect the overall population size).
# Answer:
If $PGR = Births - Deaths=0$, the number of births equals the number of deaths, so the population size is stable (from birth - death dynamics; immigration/emigration can still impact it).

### Question 11: List some examples of density - dependent factors; List some examples of Density - Independent factors
#### Density - dependent factors
# Brief Explanations:
Density - dependent factors are factors whose effects on a population change with the population's density. Examples include competition (for food, space, mates), predation (more prey means more predators can be supported, but also more predation pressure), and disease (more dense populations make it easier for diseases to spread). For example, in a dense population of rabbits, competition for grass (food) will be more intense, and a disease like myxomatosis will spread more easily.
# Answer:
Density - dependent factors examples: Competition (for food/space), Predation, Disease.

#### Density - independent factors
# Brief Explanations:
Density - independent factors are factors that affect a population regardless of its density. Examples include natural disasters (like floods, wildfires, earthquakes), climate change (such as sudden temperature drops or rises), and human - caused events like pollution spills. A flood will affect a population of frogs in a pond whether the frog population is dense or sparse.
# Answer:
Density - independent factors examples: Natural disasters (floods, wildfires), Climate change (sudden temp changes), Pollution spills.

### Question 12a: Define Renewable resource
# Brief Explanations:
A renewable resource is a natural resource that can be replenished or regenerated over time, either through natural processes or human - assisted processes, as long as the rate of use does not exceed the rate of renewal. Examples include solar energy (the sun's energy is continuously available), wind energy (wind is constantly generated by atmospheric processes), and trees (if harvested sustainably, new trees can be grown to replace them).
# Answer:
A renewable resource is a natural resource (e.g., solar energy, wind, trees) that can be replenished/regenerated over time (if used sustainably).

### Question 12b: Define Nonrenewable resource
# Brief Explanations:
A nonrenewable resource is a natural resource that is formed over extremely long geological time scales and is present in finite quantities. 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 over millions of years, and minerals like gold and copper which are mined from the Earth's crust in limited amounts.
# Answer:
A nonrenewable resource is a finite natural resource (e.g., fossil fuels, gold) formed over long time scales, not replenished in human - relevant time.

### 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 development, and environmental protection. For example, developing renewable energy sources to meet current energy needs while preserving fossil fuels for future (or using them in a limited way) and protecting ecosystems.
# Answer:
Sustainable development: Development meeting present needs without compromising future generations' ability, balancing economic, social, and environmental goals.

#### List some sustainable development strategies
# Brief Explanations:
Sustainable development strategies include: 1. Promoting renewable energy use (e.g., solar, wind power) to reduce reliance on nonrenewable fossil fuels. 2. Implementing sustainable agriculture practices (like organic farming, crop rotation) to maintain soil fertility and reduce environmental harm. 3. Encouraging recycling and waste reduction to minimize the use of raw materials and reduce landfill waste. 4. Protecting and restoring ecosystems (like reforestation, wetland restoration) to maintain biodiversity and ecosystem services.
# Answer:
Sustainable development strategies:
- Promote renewable energy (solar, wind).
- Use sustainable agriculture (organic farming, crop rotation).
- Encourage recycling/waste reduction.
- Protect/restore ecosystems (reforestation, wetland restoration).

### Question 14: What is biodiversity? What threatens it?
#### What is biodiversity?
# Brief Explanations:
Biodiversity, or biological diversity, refers to the variety of life on Earth at all levels of biological organization. This includes genetic diversity (variation within a species, e.g., different dog breeds), species diversity (the number of different species in an area, e.g., the number of bird species in a forest), and ecosystem diversity (the variety of ecosystems, e.g., forests, grasslands, oceans).
# Answer:
Biodiversity is the variety of life on Earth, including genetic (within species), species (number of species), and ecosystem (variety of ecosystems) diversity.

#### What threatens it?
# Brief Explanations:
Threats to biodiversity include: 1. Habitat loss (due to deforestation, urbanization, or conversion of land for agriculture; for example, rainforests being cleared for palm oil plantations). 2. Invasive species (exotic species introduced to an area that outcompete native species; e.g., the cane toad in Australia which has negatively impacted native wildlife). 3. Pollution (water pollution from industrial waste, air pollution from emissions, which can harm organisms and their habitats). 4. Climate change (changing temperatures and precipitation patterns can disrupt ecosystems and the species within them; e.g., coral bleaching due to rising ocean temperatures). 5. Overexploitation (overfishing, overhunting; e.g., the decline of bluefin tuna populations due to overfishing).
# Answer:
Threats to biodiversity:
- Habitat loss (deforestation, urbanization).
- Invasive species (e.g., cane toad in Australia).
- Pollution (water, air pollution).
- Climate change (e.g., coral bleaching).
- Overexploitation (overfishing, overhunting).

### 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 or heavy metal) increases as it moves up the food chain. Producers (like plants) absorb a small amount of the toxin from the environment. Herbivores eat the producers and accumulate the toxin in their bodies. Then, carnivores that eat the herbivores accumulate even more of the toxin, and so on. For example, DDT (a pesticide) becomes more concentrated in birds of prey (top carnivores) than in the insects or small animals they eat, which in turn have more DDT than the plants they consume.
# Answer:
Biological magnification is the increase in concentration of a toxic substance (e.g., DDT) as it moves up the food chain (producers→herbivores→carnivores), with top predators having the highest concentrations.

### 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?
#### Energy change as it goes up the food web
# Brief Explanations:
In a food web, the amount of energy decreases as it moves up trophic levels. This is due to the 10% rule (also known as the ecological efficiency rule), which states that on average, only about 10% of the energy available at one trophic level is transferred to the next trophic level. For example, if a plant (producer) has 1000 kcal of energy, a herbivore that eats the plant will only get about 100 kcal (10% of 1000), and a carnivore that eats the herbivore will get about 10 kcal (10% of 100).
# Answer:
Energy decreases as it moves up the food web.

#### By how much?
# Brief Explanations:
On average, about 10% of the energy at one trophic level is transferred to the next trophic level (the 10% rule). So, if the energy at trophic level $n$ is $E_n$, the energy at trophic level $n + 1$ is approximately $0.1\times E_n$.
# Answer:
On average, about 10% of the energy at one trophic level is transferred to the next (the 10% rule).

#### Where does the energy go?
# Brief Explanations:
Most of the energy (about 90% at each trophic level) is used by organisms for their life processes: respiration (to produce ATP for metabolic activities), growth and repair, and is lost as heat to the environment. For example, a deer (herbivore) uses energy from the plants it eats for running, digesting food, and maintaining body temperature (which releases heat), and only a small portion is available for a predator that eats the deer.
# Answer:
Most energy (≈90% per trophic level) is used for respiration, growth/repair, and lost as heat to the environment.

### Question 17: How does the introduction of an exotic species impact an environment?
# Brief Explanations:
The introduction of an exotic (invasive) species can have several impacts: 1. Competition: Exotic species may outcompete native species for resources like food, space, or mates. For example, the zebra mussel in North American lakes outcompetes native mussel species for food and space. 2. Predation: If the exotic species is a predator, it may prey on native species, reducing their populations. For example, the brown tree snake in Guam has caused the extinction of many native bird species. 3. Habitat alteration: Some exotic species can change the physical structure of the habitat. For example, certain invasive plants can alter soil chemistry or the fire regime of an ecosystem. 4. Disease transmission: Exotic species may introduce new diseases to native species that have no immunity. However, in some rare cases, if the exotic species is a keystone species - like, it could potentially have a positive impact, but this is less common.
# Answer:
Introduction of an exotic species can:
- Outcompete native species for resources (e.g., zebra mussel vs. native mussels).
- Prey on native species (e.g., brown tree snake in Guam).
- Alter habitats (e.g., invasive plants change soil/fire regime).
- Introduce new diseases to natives. (Rarely, may have positive impacts, but usually negative.)

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QUESTION IMAGE

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Explanation:

Question 8a: Define Limiting factor

Answer:

Question 8b: Define Carrying capacity