Question

as omnivores, humans feed at most trophic levels (although some people choose to be herbivores). as you will learn, the choices we make about our feeding patterns have significant implications for food production and ecosystem sustainability. unit task bookmark you can apply what you learned about the interactions between species in food webs in this section to the unit task described on page 156. in summary - every species occupies a unique ecological niche. - feeding relationships between organisms can be represented by food chains, food webs, and trophic levels. - energy is continuously being lost to the environment by all living organisms. check your learning 1. what is meant by the term ecological niche? describe the ecological niche of humans and of three other species. 2. explain the differences between food chains and food webs. 3. describe some possible impacts of adding or removing a species from an ecosystem. 4. as you go up from one trophic level to the next, the amount of available energy decreases. explain where the energy has gone. 5. what trophic level contains the greatest biomass in most ecosystems? explain why this occurs. 6. what trophic levels are occupied by carnivores? provide examples. 7. bison, zebra, and kangaroos are three large mammals. explain why they have similar ecological niches but cannot be shown in the same food web.

Explanation:

1. An ecological niche refers to the role and position a species has in its environment, including its interactions with other species and its use of resources. Humans have a broad - ranging ecological niche as omnivores, able to adapt to various environments and consume different types of food. For example, a lion's ecological niche is as a top - level carnivore in savanna ecosystems, preying on herbivores. A plant like grass has an ecological niche as a primary producer, using photosynthesis to convert sunlight into energy. Bees have an ecological niche as pollinators, facilitating plant reproduction.
2. Food chains represent a linear sequence of organisms where each is eaten by the next one in the chain. For example, grass → rabbit → fox. Food webs are more complex and show the interconnected feeding relationships in an ecosystem, with multiple food chains linked together. They account for the fact that organisms may have multiple food sources and be preyed upon by multiple predators.
3. Adding a species can disrupt the existing balance. For example, an invasive species may out - compete native species for resources. Removing a species can also have a cascade effect. For instance, if a keystone species like a sea otter is removed, the sea urchin population it preys on may explode, over - grazing kelp forests.
4. As energy moves up trophic levels, most of it is lost as heat during metabolic processes like respiration. Only about 10 - 20% of the energy is passed on to the next trophic level.
5. The primary producer level (usually plants) contains the greatest biomass in most ecosystems. This is because they are the base of the energy pyramid, capturing energy from the sun and converting it into biomass through photosynthesis. There needs to be a large amount of biomass at this level to support higher trophic levels.
6. Carnivores can occupy secondary, tertiary, or higher trophic levels. For example, a fox (a secondary consumer) preys on rabbits (primary consumers), while a wolf (a tertiary consumer) may prey on foxes.
7. Bison, zebra, and kangaroos have similar ecological niches as large herbivores that graze on grass. However, they cannot be shown in the same food web because they are found in different geographical regions (bison in North America, zebra in Africa, and kangaroos in Australia), so they do not interact in the same ecosystem.

Answer:

1. An ecological niche is the role and position of a species in its environment. Humans are omnivores with a broad niche. Examples of other species: Lion - top - level carnivore in savanna; Grass - primary producer; Bees - pollinators.
2. Food chains are linear, e.g., grass → rabbit → fox. Food webs are complex, interconnected networks of food chains.
3. Adding a species can cause competition; removing can have a cascade effect, like with keystone species.
4. Energy is lost as heat during metabolic processes, only 10 - 20% is passed on.
5. The primary producer level has the greatest biomass as it is the energy base.
6. Carnivores can be at secondary, tertiary, etc. levels. E.g., fox (secondary), wolf (tertiary).
7. They have similar niches as herbivores but are in different regions, so not in the same food web.