Unit 19 : Organisms and their Environment

Question 1

Define Food Chain

Answer 1

a chart showing the flow of energy (food) from one organism to the next, beginning with a producer

Question 2

Define Food Web

Answer 2

showing a network of interconnected food chains

Question 3

Define Producer

Question 4

Define Consumer

Answer 4

an organism that gets its energy by feeding on other organisms

Question 5

Define Herbivore

Answer 5

an animal that gets its energy by eating plants

Question 6

Define Carnivore

Answer 6

an animal that gets its energy by eating other animals

Question 7

Define Decomposer

Answer 7

an organism that gets its energy from dead or waste organic matter

Question 8

Define Trophic Level

Answer 8

the position of an organism in a food chain, food web or ecological pyramid

Question 9

Define Primary Consumer

Answer 9

eat vegetables

Question 10

Define Secondary Consumer

Answer 10

eat meat/drink milk

Question 11

Define Tertiary Consumer

Answer 11

eat a predatory fish, salmon

Question 12

Why do food chains have no more then 5 Trophic levels?

Answer 12

most food chains usually have fewer than five trophic levels this is because of the 10% energy law which states that only 10% of the energy is passed on so, the larger the food chains get the lesser energy is available for animals at higher trophic levels.

Question 13

What is the Energy Law?

Answer 13

in a food chain at each trophic level only 10% energy is passed on to the next trophic level and the remaining energy is lost as heat energy or undigested food and metabolic processes.

Question 14

Why is a Vegetarian Diet more Energy Efficient?

Answer 14

a vegetarian diet is more energy efficient because it provides energy directly from the producer resulting in only 10% energy loss as compared to a livestock - based diet where the livestock would have to be fed a lot of crops to provide a similar amount of energy.

Question 15

What is a Pyramid of Numbers?

Answer 15

pyramids of numbers show how many consumers there are in a given ecosystem as well as the number of producers at each trophic level. this starts with the highest number of producers who are on bottom and then in order from down to up; primary, secondary, tertiary, and quarterly

Question 16

What is a Pyramid of Biomass

Answer 16

pyramids of biomass show how much mass there is at each trophic level. this starts with the highest number of producers who are on bottom and take up the most mass and then each subsequent consumer has less mass as there isn’t enough to feed them. the biomass is counted by the average mass of a species multiplied by the number of the species.

Question 17

What is the Pyramid of Energy

Answer 17

pyramids of energy show how much energy there is at each trophic level. the sunlight is the energy that producers change into forms of sugar. then consumers take energy from producers and each other.

Question 18

Define Carbon Cycle

Answer 18

describes how carbon moves between the atmosphere, soils, living creatures, the ocean and human sources

Question 19

Define Bioaccumulation

Answer 19

the gradual gathering of substances traveling from the environment into an organism

Question 20

Define Photosynthesis

Answer 20

a process in which plants use carbon and water to make food using the energy from sunlight

Question 21

Define Fossil Fuels

Answer 21

a natural fuel formed millions of years ago from decaying organic matter

Question 22

Define Atmosphere

Answer 22

a blanket of gases surrounding the earth

Question 23

Explain the steps of the carbon cycle

Answer 23

1. carbon that is present in the atmosphere gets absorbed by plants for photosynthesis
2. plants containing carbon are consumed by animals and the carbon is bioaccumulated in their bodies
3. the animals and plants die and while decomposing the carbon is released into the atmosphere
4. carbon that isn’t released into the atmosphere is turned into fossil fuels which are used for man made activities.

Question 24

Define Nitrogen Cycle

Answer 24

the nitrogen cycle is the process in which nitrogen is cycled through the environment, moving from the atmosphere to the soil, to living things, and back to the atmosphere

Question 25

Define Nitrogen Fixation

Answer 25

nitrogen fixation is where nitrogen gas from the atmosphere is converted into nitrates by either bacteria found in soil, specific root nodules of legumes, or even when lightning strikes the ground

Question 26

Define Nitrogen Assimilation

Answer 26

nitrogen assimilation occurs when the nitrates have been absorbed by the soil and are being used to create amino acids that plants benefit from. animals then eat the plants, causing nitrogen to transfer into protein in the animal. this can pass onto other animals when feeding.

Question 27

Define Nitrogen Ammonification

Answer 27

nitrogen ammonification happens when decomposers convert the excretion and carcasses of animals into nitrogen. once returned to the soil, the nitrogen gets converted into ammonia

Question 28

Define Nitrification

Answer 28

nitrification is when the ammonium ions in the soil are converted into nitrates by nitrifying bacteria

Question 29

Define Denitrification

Answer 29

denitrification takes place when denitrifying bacteria in the soil converts nitrates back into nitrogen gas, repeating the cycle

Question 30

Define Population

Answer 30

a group of organisms of one species living in the same area at the same time

Question 31

Define Community

Answer 31

all of the populations of different species in an ecosystem

Question 32

Define Ecosystem

Answer 32

a unit containing the community of organisms and their environment interacting together

Question 33

Name and Explain 3 Factors that Affect the Rate of Population Growth

Answer 33

1. food supply - having a good food supply in both quality and quantity can enable organisms to produce more offsprings successfully. shortages in food supply can lead to starvation causing death or forced emigration, reducing the population.
2. predation - if there is large amounts of predation in a population, the rate of breeding may not be fast enough to sufficiently replace the organisms that have been eaten, causing the population to reduce.
3. disease - diseases can easily spread and may end up resulting in an epidemic. epidemics reduce population sizes rapidly and if spread globally, could become a pandemic.

Question 34

Define and Explain 4 Stages of the Sigmoid Curve of Population Growth

Answer 34

1. lag phase - there is a low amount of mature and reproducing organisms and they may be widely distributed.
2. log (exponential) phase -
   all conditions are optimum and the growth rate has reached its maximum. exponential growth occurs as the limiting factors do not affect the growth much.
3. stationary phase - limiting factors begin to slow the growth more as the population has reached something known as the “carrying capacity” (maximum population size) of the environment. when the death rate and the birth rate become equal, the curve levels and fluctuates around the carrying capacity
4. death phase - this is when the death rate becomes larger then the birth rate due to the factors which affect population growth like competition, lack of food, etc.