Correct Answer: Option 3, They recycle chemicals from dead organisms.

Fungi and bacteria are principal decomposers that keep the nutrient balance in ecosystems, which is essential for plant and animal growth. They play an important role in nutrient cycling, or the endless recycling of chemical elements that occurs between organisms and their nonliving surroundings. Fungi and bacteria secrete enzymes that degrade organic material into inorganic nutrients and minerals, which are then returned to the environment, ready to be absorbed by living organisms.

Option 1 is incorrect. The decomposers recycle and break down organic materials, which are returned to the abiotic environment in forms that can be used by plants, but not as energy.

Option 2 is incorrect. They release inorganic products like carbon dioxide and ammonia, not oxygen.

Option 4 is incorrect because what they synthesize are inorganic products from organic nutrients, not the other way around.

Correct Answer: Option 4 glucose

The solar energy is used up by photoautotrophs to produce glucose and oxygen. The living cell uses glucose as a source of energy and metabolic intermediate. Glucose is then processed through respiration to form ATP.

Protein, fat and DNA are not products of photosynthesis, hence, options 1, 2, nd 3 are invalid.

Correct Answer: Option 4 lost as heat to the environment

As energy flows through an ecosystem, much of it is dissipated before it can be consumed by organisms at the next level. Of the N calories of energy absorbed by an organism, one-sixth is used for growth, and the rest is passed as feces (which will be consumed by decomposers) or used for cellular respiration. The energy used for respiration is lost from the ecosystem; thus, while solar radiation is the ultimate source of energy in most ecosystems, respiratory heat loss is the ultimate sink.

Correct Answer: Option1 The ecosystem is most likely unstable.

The base of this pyramid should be largest energy source because it is the primary source of energy in the system. Since much of the energy is lost during the transfer to the next trophic level, this ecosystem might not be sustained in the long term. Thus, option 2 is invalid.

Option 3 is incorrect. The herbivore populations will not continue to increase due to scarcity of their food source, the algae.

Option 4 is false. There is less amount producers than the consumers, based on the diagram.

Correct Answer: Option 4 The rabbits had no natural predators in Australia.

The rabbits were able to increase in population because there were no organisms that preyed and endangered their initial population which was quite small.

If the rabbits were affected by limiting factors then the population would not increase exponentially. Therefore, option 1 is false.

Option 2 is incorrect. The rabbits naturally reproduce sexually, not asexually.

If the rabbits were not able to adapt to the environment of Australia, then their population would not increase exponentially. Hence, option 3 is incorrect.

Correct Answer: Option 2 The smaller the crocodile is, the larger the prey.

The smaller crocodiles composing the group A preferred to eat smaller prey like insects, frogs, and spiders. Therefore, statement 2 is false.

Option 3 is incorrect. Group B showed the lowest (negligible) preference for birds and reptiles.

Crocodiles of group A preferred to eat more insects than the other organisms available as prey. If the insects will be eradicated through the use of insecticides, the feeding habit of the small crocodiles will be affected. Thus, option 4 is not the false statement.

This statement is true because it was recorded that crocodiles from group C preferred to eat mammals, reptiles, and fish. If the population size of fish would decrease, the feeding habit of group C will be affected. Hence, option 1 is not the correct answer.

Correct Answer: Option 4 The rate of reproduction exceeds the death rate

The steep slope of section II indicates the logistical growth in the number of organisms. There is less occurrence of death during this period of time.

Carrying capacity is the maximum population size that can be supported by the available resources. The population has not yet reached the carrying capacity of the population because it still continued to increase in number, meaning the environment can still support the increase in population. Thus, options 1 and 3 are false.

Option 2 is incorrect because the slope is steeper in section II than in section I.

Correct Answer: Option 1 they most likely do not compete for nesting sites because they occupy different niches.

There is no competition because even though they prefer the same type of tree, they put their nests at entirely different heights. This means that they prefer different niches. Option 4 is incorrect.

Their reproductive behavior has no effect on the competition of sites because the prefer nesting at different niches. Hence, option 2 is incorrect.

Option 3 is incorrect because there is insufficient data to infer about the type of nest.

Correct Answer: Option 3

Sand eels are at the bottom of this particular food web. Sand eels are both consumed by herring and cod. Herring is eaten by tuna, while cod is eaten by seabirds. When the herring were overharvested, its consumer also faded. The cod probably feed on cods and this is the reason why its population decreased when sand eels were overharvested. The seabirds decreased in number because they feed on the cods, which also deceased.

Correct Answer: option 3 both food chain A and food chain B

Decomposers form a link with all the trophic levels of a food chain. When these organisms die, the decomposers act on them by secreting enzymes that digest organic material and then absorb the breakdown products. After the organic materials are recycled and broken down, the products and returned to the abiotic environment in forms that can be used by plants. Both food chains starts with the plants (aquatic plant and grass).