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Answers to Midterm Study Guide  

Energy in Ecosystems

1. 

A mushroom grows on a rotting log. As a result, water and nutrients from the log are released into the soil. What type of organism is the mushroom?

 

 

     
     
     
     

Write your response here:









2. 

In a marine ecosystem, phytoplankton perform photosynthesis. Krill eat the phytoplankton, and seals, whales, and sea birds feed on the krill. Finally, great white sharks hunt and eat the seals.

Which of these organisms are consumers?

     
     
     
     

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3. 

Examine the food web below. What might happen to this food web if the ecosystem it represents experienced a serious climatic change that caused most of the ecosystem's streams to dry up?

 

 

     
     
     
     

Write your response here:








4. 

The following diagram represents the Antarctic food web.

 


If fish populations in the Antarctic were to decline, what would be the best way for the smaller toothed whales to adapt?

     
     
     
     

Write your response here:












5. 

Which of the following living things would be found closest to the beginning of a food chain?Why?

 

 

A.

scorpion

 

B.

mushroom

 

C.

caterpillar

 

D.

coyote

Write your response here:



6. 

The food chain below shows an example of how energy flows through an ecosystem.

 

What is the ultimate source of all of the energy that flows through this food chain?

 

     
     
     
     

Write your response here:




7. 

Which of the following remains constant in an ecosystem? Explain your Reasoning?

 

 

A.

number of organisms

 

B.

number of species

 

C.

weather patterns

 

D.

amount of matter

Write your response here:









8. 

Producers in an ecosystem store energy by converting carbon dioxide and water into energy-rich carbon compounds called __________.

 

     
     
     
     

Write your response here:


 

 

 

 


9. 

A diagram of an Australian grassland food web is shown below.

 

Which type of organism is part of the food web, but does not appear in the diagram? What role do they fullfill

 

     
     
     
     

Write your response here:






10. 

What does the following diagram illustrate?

AlgaeMinnowsSalmonBear

 

     
     
     
     

Write your response here:


11. 

Which of the following series shows a correct path of energy flow in a desert food chain? Justify your answer?

 

 

A.

lizard fly spider scorpion

 

B.

fly spider scorpion lizard

 

C.

scorpion spider lizard fly

 

D.

spider lizard fly scorpion

Write your response here:


12. 

 

According to the food web shown, which group below lists only secondary consumers? How do you know?

 

 

A.

penguins, other seals, phytoplankton

 

B.

krill, leopard seal, smaller toothed whales

 

C.

fish, carnivorous zooplankton, birds

 

D.

elephant seal, fish, other herbivorous zooplankton

Write your response here:



13. 

Which type of organism generates oxygen and makes up the lowest trophic level in an energy pyramid?

 

 

A.

herbivores

 

B.

producers

 

C.

omnivores

 

D.

consumers

Write your response here:



 

 


14. 

The diagram below shows a possible amount of energy, in kilocalories, available in the organisms at each level of an ecosystem's food chain.

 

According to the law of conservation of energy, energy can neither be created nor destroyed. If this is true, why is there less energy in the top of the food chain shown above than there is in the bottom of the food chain?

 

     
     
     
     

Write your response here:






15. 

What does the following diagram illustrate?

 

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16. 

Which level in a food web contains the highest amount of total available energy?

 

     
     
     
     

Write your response here:





17. 

Food webs and food chains are two different ways that ecologists illustrate the interrelatedness of organisms in an ecosystem. What is the relationship between a food web and food chain?

 

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18. 

A food chain is a model that represents how energy and matter are transferred through an ecosystem.

Typically, a food chain has five or fewer links because

 

     
     
     
     

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19. 

Examine the energy pyramid below.

 

Is it possible for the top level to be wider than the level before it?

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20. 

Decomposers are a necessary part of a healthy ecosystem because they...

Write your response here:















 

Answers

1.

Bdecomposer

2.

Csharks, krill, seals, whales, and sea birds

3.

DThe bears would starve.

4.

Beat more baleen whales

5.

Ccaterpillar

6.

Cthe Sun

7.

Damount of matter

8.

Ccarbohydrates

9.

Cdecomposers

10.

Aa food chain

11.

Bfly spider scorpion lizard

12.

Cfish, carnivorous zooplankton, birds

13.

Bproducers

14.

AEnergy leaves the food chain as heat.

15.

Dan energy pyramid

16.

Dproducer

17.

DFood webs illustrate multiple interrelated food chains.

18.

Dthe amount of energy available decreases with the addition of each link.

19.

CNo, it is not possible for an ecosystem to support more predators than prey.

20.

Breturn nutrients to the environment so matter and energy can begin another cycle.

Explanations


1.


The mushroom is a decomposer. Decomposers help complete the water, carbon, nitrogen, and oxygen cycles by releasing matter from dead plants and animals into the soil, water, and atmosphere.

Producers can incorporate the released matter into their structures and thus start another cycle of matter and energy.


2.


In the ecosystem described, all of the organisms other than phytoplankton are consumers.

Krill are primary consumers. Seals, whales, and sea birds are secondary consumers. Sharks are tertiary consumers.

Since phytoplankton make their own food through photosynthesis, they are producers.


3.


In the event that the climate of this ecosystem became more arid and many of the streams dried up, all of the organisms that relied on aquatic life for food would either starve, be forced to migrate, or if possible be forced to use other organisms for a food source. In the food web shown, many of the terrestrial animals rely on both aquatic and other terrestrial animals for food, so while their populations would be affected, they do not have as great a chance of starving as a terrestrial population that relied solely on aquatic life for food, such as the population of bears.


4.


Smaller toothed whales are secondary consumers of fish. If the fish population declined, the populations of leopard seals, elephant seals, and penguins—animals which make up a large portion of the whales' diet—would likely also decline.

To survive, the smaller toothed whales would have to eat more animals that feed primarily on krill instead of fish, such as seals (not leopard or elephant seals) and baleen whales.


5.


Primary producers (plants) typically occur at the beginning of all food chains. The next organisms are the primary consumers, or livings things that consume plants. A caterpillar is an example of a primary consumer. A scorpion is a secondary consumer, which feeds on other consumers. Mushrooms are decomposers; these organisms feed on dead plant and animal material throughout the food chain.


6.


Food chains describe the eating relationships and energy flow between species within an ecosystem. The ultimate source of energy for almost all ecosystems on Earth is the Sun.

Producers, such as plants, receive energy from the Sun and make their own food (i.e., glucose sugar) through the process of photosynthesis. Producers are at the beginning of food chains because all of the other organisms in food chains depend on the food energy that they make.


7.


The amount of matter remains constant as it cycles through an ecosystem. While matter may change forms, it cannot be either created or destroyed.

Producers use sunlight to convert carbon dioxide, water, and nutrients into carbohydrates and other types of biomolecules. Consumers convert matter obtained by eating producers or other consumers into sugars, starches, lipids, and proteins.

Decomposers break down waste and the remains of dead plants and animals. Through this process, water and nutrients are returned to the soil and the atmosphere. These raw materials can then be used in another cycle.


8.


During photosynthesis, producers use the energy in sunlight to turn carbon dioxide and water into carbohydrates such as glucose and cellulose. Energy that is stored in these carbohydrates can be released for use by organisms that eat the plant material.


9.


Decomposers are crucial to the existence of all ecosystems, but they do not appear in this food web diagram. Decomposers feed on the bodies of all the organisms in a food web.

Fungi and bacteria are examples of decomposers.


10.


The path of energy through the trophic levels of an ecosystem is called a food chain. All food chains begin with a producer.


11.


In a food web, each organism is consumed by the following organism. A fly will not eat a spider, scorpion, or lizard, so it must be at the bottom of this food chain.


12.


Secondary consumers are the organisms that eat the primary consumers. Primary consumers eat the producers (phytoplankton). The only choice that lists only secondary consumers is fish, carnivorous zooplankton, and birds.


13.


Producers are plants or other photosynthetic organisms that generate oxygen as a byproduct of photosynthesis.

Producers make up the lowest trophic level in the energy pyramid for any ecosystem because they make food for themselves and the animals that consume them. There are more organisms in this trophic level than in any other.


14.


The law of conservation of energy is universal. Energy cannot be created nor destroyed. There is less energy available in the top of the food chain than there is in the bottom because organisms all along the food chain are using the energy, and some of the energy leaves the food chain as heat. The heat energy is dispersed into the surrounding environment.


15.


Ecologists often illustrate the flow of energy through ecosystems with an energy pyramid, a diagram in which trophic levels are represented by stacked blocks. The size of each block is determined by the amount of energy stored in the organisms at that trophic level.


16.


Energy first flows into a food web through primary producers. Moving up each of the trophic levels, the available energy reduces by around ten percent each time. Thus, the amount of energy available to consumers or decomposers is much less than that of the producers.


17.


A food chain is a simplified version of how energy flows through an ecosystem. While a food chain does show the energy-flow relationships between one kind of organism on each trophic level, a food web will illustrate many different organisms on the same trophic level as well as the energy-flow relationship within and between each of these levels. In essence, a food web is a depiction of many different food chains.


18.


With each addition of a food chain link, less energy is available for use by the animals or organisms in that link.

This is because not all available food in the previous link is captured or collected, not all captured food is eaten, not all food eaten is digested, and not all energy in the food digested is used to power body processes. (Much is lost as heat.) When the number of food chain links approaches five, there is simply not enough energy left to transfer to another link.


19.


The energy stored by the organisms at each trophic level is about one-tenth of the energy stored by the next level. Most of the stored energy in an ecosystem is in plants and other producers. The primary consumers in the ecosystem have only one-tenth of the energy that is stored in the producers. That is because an ecosystem cannot maintain equilibrium if there are more predators than prey.

Energy pyramids model this relationship by displaying producers as a broad base that supports the other interactions in the system. The decreasing size of the other tiers demonstrates that the amount of energy available to each trophic level decreases as you move up the pyramid.


20.


Decomposers return nutrients to the environment so matter and energy can begin another cycle.

Decomposers break down dead plant and animal material into small inorganic molecules, such as phosphates and nitrates. These molecules enter the soil and water where they are used by plants to build new structures.

If plants did not have access to this inorganic material, the plants could not grow. Soon, life in the ecosystem would cease because animals would not have access to a food supply.

Evolution & Natural Selection

1. 

In 1859, the English naturalist Charles Darwin published a book entitled On the Origin of the Species. One of the major ideas that was presented in his book was the theory of natural selection. What was another idea that was presented in his book?

 


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2. 

Genetic variation occurs in all organisms. Bacteria that cause ear infections, for example, are genetically similar and produce the same effect, but some variations may exist such that some of the bacteria might be resistant to antibiotics, while others are not. Which of the following would increase the antibiotic resistant bacterial populations?


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3. 

Comparative biochemistry is the study of similarities and differences in _______ among organisms.


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5. 

A chance mutation causes a cheetah to be born with very short front limbs. What will be the most likely result of this mutation?


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6. 

According to modern scientific theory, which of the following organisms appeared first?Explain.

 

 

A.

mammals

 

B.

humans

 

C.

land plants

 

D.

microorganisms


Write your response here: 



7. 

A cold frost has temporarily killed most of the terrestrial vegetation in an area. Which of the following populations would be most affected by the cold frost?Explain

 

A.

humans

 

B.

fish

 

C.

rabbits

 

D.

vultures

 
Write your response here: 


8. 

Which of the following is an adaptation that would make the most sense in a fully-submerged water plant? Justify

 

 

A.

The ability to expel carbon dioxide from its roots.

 

B.

The ability to store water in its stem.

 

C.

The ability to grow rigid roots and stems.

 

D.

The ability to live in low light conditions.


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9. 

In tropical rainforests, the vegetation is often so dense that very little sunlight can reach the forest floor. What types of adaptations that some rainforest plants have developed as a result?


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10. 

Some organisms have favorable traits that are well-suited to the environment at hand. Organisms with this advantage are more likely to thrive, reproduce, and pass their traits to future generations than organisms without favorable traits.

This process is known as


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11. 

Most heritable differences are due to


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12. 

Some organisms that appear to be very different from other organisms are in fact quite similar anatomically. Scientists believe whales evolved from land mammals for many reasons including a few internal functionless hind-limb bones found in whales’ bodies. What is the term for a functionless anatomical structure that is evidence of an organism’s evolutionary past?


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13. 

Succulent plants have fleshy leaves with thick surface layers. These characteristics help the plant


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14. 

Which of the following may have been an advantageous adaptation for the jack rabbit?

I.

long ears to help them hear better

II.

big feet to help them move faster and farther

III.

teeth to help them protect themselves


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15. 

Based on the theory of evolution, if a population possesses a large amount of genetic variety, what level of variety can be expected in the future for that same population?


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16. 

Morphological adaptations are structural traits that promote an organism's success in a specific environment. Which of the following are morphological adaptations?

I.

a hummingbird's elongated beak

II.

the thorns on a rose

III.

digestive enzymes


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17. 

 

The figure above shows plates made from a culture growing bacteria during specified generations. The culture has white and dark bacteria. After generation 1, scientists applied an experimental drug and kept the experimental drug in the culture during successive generations. Which statement best explains the results of the experiment?


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18. 

Gregor Mendel's experiments with peas led him to conclude several important things about inheritance. Which of the following of Mendel's conclusions is a necessary foundation for Darwin's theory of natural selection?


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19. 

What are likely side effect of the over usage of pesticides?


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20. 


W.


X.


Y.


Z.

The figures above show the limb structure of four different types of crawling animals. Which animal evolved from a different ancestor? Justify your answer.


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Answers

1.

Male organisms often possess special features that make them more attractive to female organisms.

2.

an overusage of antibiotics

3.

DNA sequence

4.

Protista

5.

The cheetah will not be able to run as fast.

6.

microorganisms

7.

rabbits

8.

The ability to live in low light conditions.

9.

the ability to germinate and grow on top of other plants

10.

natural selection.

11.

gene shuffling that occurs during the production of gametes.

12.

vestigial structure

13.

conserve water.

14.

I and II only

15.

The population will increase in variety over time.

16.

I and II only

17.

The dark bacteria showed resistance to the drug.

18.

There are alternate versions of a gene.

19.

Pesticide-resistant pests will survive, reproduce and flourish.

20.

X




 

Explanations


1.


According to Darwin's theory of natural selection, organisms with favorable characteristics have an increased chance of survival over other organisms with less favorable characteristics.

In his book, On the Origin of the Species, Darwin elaborated on this concept by proposing that male organisms often possess special features that make them more attractive to female organisms. According to Darwin, special features increase the reproductive success of the male organisms.


2.


The overusage of antibiotics would cause a depletion in those bacteria that are sensitive to the antibiotics. The antibiotic-resistant bacteria that remained after exposure would then be free to continue to reproduce thereby increasing their populations.


3.


One of the ways scientists judge whether two species are related is through comparative biochemistry--the study of organisms' DNA sequences.

While each species has its own unique DNA sequence, sequences of related organisms will be more similar than sequences of unrelated organisms.


4.


Today, eukaryotes are single or multi-celled organisms, but the first eukaryotes were only single-celled. They were differentiated from prokaryotes by their nucleus. These nucleus-bearing, single-celled organisms were the ancestors of modern-day protists as well as all other forms of eukaryotic life.


5.


Chance mutations can sometimes cause genotypic or chromosomal variations. These variations can, in turn, result in phenotypic variations or different visible physical traits.

A cheetah born with short front legs will most likely not be able to run as fast as a normal cheetah. Consequently, the cheetah will not be able to catch as many prey and may die from starvation. Adaptations, such as this one, that do not benefit an organism will most likely be eliminated from the genetic pool due to natural selection.


6.


According to modern scientific theory, the Earth is approximately 4.6 billion years old.Microorganisms appeared first - 3.4 million years ago. Land plants appeared 400 million years ago. The first mammals and dinosaurs appeared 225 million years ago, and humans appeared last - 2 million years ago.


7.


Fish, humans, and vultures are able to eat other items besides plants. However, since rabbits feed directly and exclusively on plants, their population would be affected the most by the cold frost. If the cold frost were to continue, the rabbits would have to either migrate to an area where there is more vegetation, or adapt and learn to eat something new.


8.


Plants that are totally submerged in water receive very diffuse light. These plants have adapted the ability to collect what little light they receive to carry out photosynthesis.


9.


Certain rainforest plants have developed an ability to grow on top of other plants, thus allowing them more sunlight exposure. These types of plants are called epiphytes.


10.


Favorable traits are traits that promote an organism's success in a particular environment. Organisms with favorable traits are more likely to thrive, survive, and reproduce than organisms without favorable traits. In this way, nature "selects" which traits (or even which types of organisms) will continue to exist in a population.


11.


Many factors can cause a change in a gene over time. However, most heritable differences are due togene shuffling that occurs during the production of gametes. Gametes are produced when cells undergo meiosis.

Mutations or changes in DNA sequences can occur spontaneously, but this happens infrequently.


12.


Vestigial structures are structures in an organism that are reduced in size and function and that may have been complete and functional in the organism’s ancestors. Homologous structures are anatomical structures that share a common ancestry.


13.


Succulent plants have features that allow them to survive in dry conditions. The fleshy leaves of succulents store water. The thick, waxy surface layers of the leaves prevent the loss of stored water, which helps them conserve water.


14.


Long ears for hearing and big feet for moving are two adaptations that have helped the jack rabbit survive.

Rabbits do not usually use teeth as a means of protection.


15.


Evolution builds on what already exists. A population that possesses a large amount of variety in its current state will tend to increase in variety over time.

Each variation can branch out in many directions, so evolution will not tend to progress in any one single direction.


16.


A hummingbird's elongated beak and a rose's thorns are examples of morphological adaptations because both are structural traits which help the organisms thrive in their environment. The hummingbird's long beak makes it possible to reach nectar that forms deep within elongated flowers. Rose thorns promote the rose's success by protecting it from attack by animals.

Production of digestive enzymes is a physiological adaptation rather than a morphological one because it does not involve the formation of special structural traits.


17.


The frequency of dark bacteria in the population was low. The presence of the drug reduced the frequency of the white bacteria and increased the frequency of the dark bacteria. You can conclude that the dark bacteria were resistant to the drug and were able to reproduce successfully over time.


18.


Mendel's realization that there are alternate versions of genes helped to explain why offspring could be similar to, yet different from, their parents. This idea that there is genetic diversity, even between an offspring and a parent, is an important feature in the process of natural selection. Without genetic variation, natural selection could not occur.


19.


The overuse of pesticides allows the organisms with a higher tolerance for pesticides to survive in greater numbers. The pesticide resistant organisms can then reproduce to create more pesticide resistant organisms.


20.


Animal X has each digit attached to a compound wrist bone, while all the others have 3 digits attached to a single wrist bone. This suggests that animal X evolved from a different ancestor from the other three.

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