Biodiversity is the variety of life on Earth, from genes and species to entire ecosystems. This cheat sheet helps students connect biodiversity to ecosystem health, human needs, and environmental decision-making. It is useful for reviewing conservation biology, endangered species, habitat loss, and sustainability.
Students need these ideas to understand how human actions can protect or reduce the stability of natural systems.
The most important concepts include genetic diversity, species diversity, ecosystem diversity, ecosystem services, and the major causes of biodiversity loss. Students should recognize that high biodiversity usually increases resilience, which helps ecosystems recover from disturbance. Key conservation strategies include protecting habitats, restoring damaged ecosystems, reducing pollution, controlling invasive species, and using resources sustainably.
Simple measurements such as species richness, species evenness, and biodiversity indexes help scientists compare ecosystems.
Key Facts
- Biodiversity includes genetic diversity, species diversity, and ecosystem diversity.
- Species richness is the number of different species in an area.
- Species evenness describes how evenly individuals are distributed among the species in a community.
- A simple biodiversity index can be estimated as biodiversity index = number of species / total number of individuals.
- The main threats to biodiversity are habitat loss, invasive species, pollution, population growth, overharvesting, and climate change.
- Ecosystem services include provisioning services such as food and water, regulating services such as climate control, supporting services such as nutrient cycling, and cultural services such as recreation.
- Conservation can be in situ, which protects species in their natural habitats, or ex situ, which protects species outside their natural habitats.
- The IUCN conservation status scale includes categories such as least concern, vulnerable, endangered, critically endangered, extinct in the wild, and extinct.
Vocabulary
- Biodiversity
- Biodiversity is the variety of living things in an area, including variation in genes, species, and ecosystems.
- Ecosystem service
- An ecosystem service is a benefit that humans receive from nature, such as clean water, pollination, soil formation, or flood control.
- Endangered species
- An endangered species is a species that is at high risk of becoming extinct in the near future.
- Invasive species
- An invasive species is a nonnative organism that spreads in a new area and causes harm to native species, ecosystems, or human activities.
- Habitat fragmentation
- Habitat fragmentation is the breaking of a large habitat into smaller, isolated patches, often because of roads, farms, or development.
- Conservation
- Conservation is the protection, management, and restoration of natural resources and biodiversity.
Common Mistakes to Avoid
- Confusing species richness with species evenness is wrong because richness counts how many species are present, while evenness describes how balanced their populations are.
- Assuming a large population always means high biodiversity is wrong because biodiversity depends on the variety of species and their distribution, not only the total number of organisms.
- Thinking all nonnative species are invasive is wrong because a species is invasive only when it spreads and causes ecological, economic, or health harm.
- Ignoring habitat fragmentation is wrong because small isolated habitat patches can reduce breeding opportunities, limit food access, and increase extinction risk.
- Focusing only on endangered animals is wrong because conservation also protects plants, fungi, microbes, habitats, ecosystem services, and genetic diversity.
Practice Questions
- 1 A forest survey finds 8 species and 200 total individual organisms. Using biodiversity index = number of species / total number of individuals, what is the biodiversity index?
- 2 Two ponds each have 100 organisms. Pond A has 5 species with 20 organisms in each species. Pond B has 5 species, but one species has 80 organisms and the other four have 5 each. Which pond has greater species evenness?
- 3 A grassland had 30 native plant species before development. After a road and housing project, only 18 native plant species remain. How many native plant species were lost?
- 4 Why can protecting one large connected habitat be more effective for biodiversity than protecting several small isolated habitat patches?
Understanding Biodiversity & Conservation
Biodiversity works like a network rather than a list of separate organisms. Plants capture energy from sunlight. Herbivores eat plants.
Predators affect herbivore numbers. Fungi, bacteria, and insects break down dead material and return nutrients to soil and water. A change in one part of this network can spread outward.
If a pollinating insect disappears, some flowering plants may produce fewer seeds. Animals that depend on those plants may then lose food or shelter.
This is why a species that seems small or unpopular can still have an important ecological role. Predators, decomposers, and pollinators are often especially important because they influence many other species.
Genetic variation matters most when conditions change. Individuals in the same species are not exact copies. Some may tolerate drought, resist a disease, or survive warmer temperatures better than others.
When a population becomes very small and isolated, close relatives are more likely to breed. This can reduce genetic variation over generations. The population may then be less able to survive a new disease, a heat wave, or a change in food supply.
Wildlife corridors can help with this problem. A corridor is a connected strip of habitat that allows organisms to move between separated areas. Examples include tree-lined routes between forests, safe road crossings for animals, and connected river habitats for fish.
Biodiversity measurements need careful interpretation. Two sites can contain the same number of species but still differ greatly in ecological condition. In one site, each species may have similar numbers of individuals.
In another, one species may make up nearly the whole population while the others are rare. A simple index gives a quick comparison, but it does not show every detail. Scientists must consider the size of the area sampled, the season, the sampling method, and whether rare organisms were missed.
A pond survey in spring can produce different results from a survey at the same pond in late summer. Repeated sampling makes conclusions more reliable. Students should pay attention to what the data can support and what it cannot prove.
Conservation decisions often involve trade-offs because land, water, and money are limited. Protecting a large, intact habitat usually helps many species at once, but some species need specific actions. For example, a threatened bird may need nesting sites protected during breeding season.
A plant may need invasive weeds removed before it can grow again. Zoos, seed banks, and captive breeding programs can prevent total loss, yet they cannot fully replace healthy natural habitats. Local choices matter too.
Using less pesticide can protect insects and water quality. Planting native species can provide food for local wildlife.
Reducing waste, choosing sustainably harvested products, and supporting habitat protection all reduce pressure on living systems. Conservation is most effective when prevention begins before a population becomes critically small.