19. Which of the following terrestrial biomes has the highest animal diversity?
(A) Tropical forest
(B) Savanna
(C) Chaparral
(D) Tundra
Terrestrial Biome with the Highest Animal Diversity
Detailed Explanation of the Correct Answer
Among all the options given, the tropical forest has the highest animal diversity. Therefore, option (A) is the correct answer.
Tropical forests, particularly tropical rainforests, are among the most biologically diverse terrestrial ecosystems on Earth. They support an enormous variety of animals, including insects, birds, mammals, reptiles, amphibians, and many other groups. The combination of warm temperatures, high rainfall, abundant food resources, complex vegetation, and relatively stable environmental conditions creates ideal circumstances for the survival and diversification of a very large number of species.
Animal diversity does not depend only on the total amount of food available in an ecosystem. It is also strongly influenced by the number of different habitats and ecological niches available. Tropical forests have an extremely complex vertical structure, with organisms living on the forest floor, in the understory, along tree trunks, within the canopy, and in the emergent layer. Each of these regions provides different environmental conditions and resources, allowing many species to coexist.
In comparison, savannas, chaparral regions, and tundra biomes experience stronger environmental limitations such as seasonal drought, fire, low rainfall, or extreme cold. These factors generally reduce the number of species that can survive successfully. For this reason, tropical forests have the highest animal diversity among the terrestrial biomes listed in the question.
Why Tropical Forests Have Such High Animal Diversity
Warm and Relatively Stable Climate
Tropical forests generally occur in regions with warm temperatures throughout the year. Unlike temperate or polar environments, these ecosystems do not experience severe winters or prolonged periods of freezing conditions.
A relatively stable climate allows animals to remain active, feed, reproduce, and interact throughout much of the year. Over long evolutionary periods, climatic stability has also allowed species to become highly specialized for particular habitats, food sources, and ecological roles.
When many species specialize in different resources, direct competition can be reduced. This ecological specialization helps support the coexistence of an exceptionally large number of animal species.
High Rainfall and Abundant Water
Tropical forests generally receive high annual rainfall, which supports dense and continuous plant growth. Water is essential for plant productivity, and high plant productivity ultimately supports complex food webs.
Plants provide fruits, seeds, leaves, nectar, pollen, bark, roots, and other resources for herbivores. These herbivores then support predators and parasites. Dead organic matter supports decomposers and detritivores.
Therefore, abundant rainfall indirectly contributes to high animal diversity by supporting a large and continuous biological resource base.
High Primary Productivity
Tropical forests receive abundant solar energy and generally have favorable conditions for photosynthesis throughout the year. This supports high levels of biological productivity.
High plant productivity provides energy for numerous herbivores, which in turn support carnivores, parasites, scavengers, and decomposers. As energy moves through the food web, a large number of ecological interactions develop.
The availability of diverse food resources is one of the major reasons why tropical forests can support so many different animal species.
Complex Vegetation Structure
One of the most important reasons for the extraordinary animal diversity of tropical forests is their complex vegetation structure. Tropical forests are not uniform habitats. Instead, they contain multiple vertical layers.
Animals may occupy the forest floor, shrub layer, understory, canopy, or emergent layer. Some species spend almost their entire lives high in the canopy, while others are restricted to leaf litter or soil.
This vertical stratification creates numerous ecological niches. Because different species can use different parts of the forest, many animals can coexist within the same geographical area.
Large Number of Ecological Niches
An ecological niche describes how an organism uses resources and interacts with its environment. Tropical forests provide an enormous variety of niches because they contain many types of food, shelter, breeding sites, microclimates, and physical structures.
One species may feed on a particular type of fruit, another may specialize in nectar, and another may consume insects living under tree bark. Some predators hunt in the canopy, while others search for prey on the forest floor.
This high level of ecological specialization allows a large number of species to live together without depending on exactly the same resources.
Option (A): Tropical Forest
The tropical forest is the correct answer because it supports the highest animal diversity among the terrestrial biomes listed.
Tropical forests occur mainly in warm regions near the equator and are characterized by high rainfall, dense vegetation, high biological productivity, and complex habitat structure. These conditions support enormous numbers of animal species.
Insects represent a particularly large component of tropical forest biodiversity. In addition, these forests contain numerous species of birds, primates, bats, reptiles, amphibians, and other animals.
The three-dimensional structure of tropical forests creates habitats from the ground to the upper canopy. This allows animals with very different ecological requirements to coexist.
Therefore, option (A) is correct.
Option (B): Savanna
A savanna is a tropical or subtropical grassland characterized by grasses with scattered trees and shrubs. Savannas support a high diversity of animals and are especially famous for large herbivorous mammals and their predators.
Animals commonly associated with savanna ecosystems include grazing mammals, browsing mammals, carnivores, birds, reptiles, and numerous insects. The combination of grasses and scattered woody vegetation creates several different habitats.
However, savannas experience pronounced seasonal changes in rainfall. Long dry seasons, periodic drought, grazing pressure, and frequent fires can limit vegetation complexity and resource availability.
Although savannas may contain impressive numbers of large mammals, the total animal species diversity is generally lower than that of tropical forests. Tropical forests provide more habitat layers, more microhabitats, and a greater variety of ecological niches.
Therefore, option (B) is incorrect.
Option (C): Chaparral
The chaparral biome is characterized by dense shrubs, hot and dry summers, and mild, wetter winters. It commonly occurs in regions with a Mediterranean-type climate.
Animals living in chaparral ecosystems must cope with seasonal water shortages, high summer temperatures, and periodic fires. These environmental conditions support specialized communities of mammals, birds, reptiles, insects, and other organisms.
Fire plays an important ecological role in chaparral ecosystems. Many plants and animals have adaptations that allow them to survive or recover after fire. However, the combination of limited water availability and strong seasonal stress restricts the total number of species that can survive in these environments.
The vegetation structure of chaparral is also less vertically complex than that of tropical forests. Consequently, fewer ecological niches are available.
Therefore, option (C) is incorrect.
Option (D): Tundra
The tundra has the lowest animal diversity among the major terrestrial biomes listed in this question. It occurs mainly in extremely cold regions where low temperatures, short growing seasons, and frozen soil strongly limit biological productivity.
The tundra supports animals adapted to severe environmental conditions. Many species possess thick fur, layers of body fat, seasonal migration patterns, or other adaptations that help them survive extreme cold.
During the short summer season, migratory birds and insects may become abundant. However, only a limited number of species can tolerate the harsh conditions throughout the year.
Low temperatures, limited vegetation, a short growing season, and low primary productivity reduce the number of ecological niches available. As a result, tundra ecosystems have much lower animal diversity than tropical forests.
Therefore, option (D) is incorrect.
Comparison of Animal Diversity Among the Given Biomes
Among the four options, tropical forests provide the most favorable combination of climatic stability, energy availability, water, food resources, and habitat complexity.
The tropical forest has extremely high animal diversity because of its warm climate, high rainfall, dense vegetation, and large number of ecological niches.
The savanna supports diverse animal communities, including many large mammals, but strong seasonal changes and a simpler vegetation structure limit overall species diversity compared with tropical forests.
The chaparral contains specialized animals adapted to drought and fire, but environmental stress limits the total number of species.
The tundra has the lowest diversity because extreme cold, low productivity, and a short growing season restrict the number of animals capable of surviving there.
Thus, the general comparison among the given options is:
Tropical forest > Savanna > Chaparral > Tundra
The most important conclusion is that tropical forests support the greatest animal diversity because they provide the highest variety of habitats and ecological opportunities.
Relationship Between Habitat Complexity and Animal Diversity
Habitat complexity is one of the strongest factors influencing animal diversity. A structurally simple habitat provides a limited number of places for organisms to feed, hide, reproduce, and avoid predators. In contrast, a structurally complex habitat creates numerous ecological opportunities.
Tropical forests contain trees of different heights, vines, epiphytes, fallen logs, leaf litter, tree holes, water-filled plant structures, and multiple canopy layers. Each structure can support different groups of organisms.
This large number of microhabitats allows species to divide available resources and occupy specialized niches. Consequently, tropical forests can support far more animal species than biomes with simpler vegetation structures.
Final Answer
The terrestrial biome with the highest animal diversity is the tropical forest.
Therefore, the correct answer is:
(A) Tropical forest
Tropical forests support exceptionally high animal diversity because of their warm and stable climate, abundant rainfall, high biological productivity, complex vegetation structure, and enormous variety of ecological niches.
