Background for Teachers
TPW Magazine, November 2009
This month we feature a fun way to look at ecosystems, structure, function and adaptations.
Teeth and claws provide clues to animals' diet and feeding behavior. For example, having sharp teeth for tearing, and grasping claws for a firm grip, helps some predators capture, kill and eat prey. These adaptations, however, would make it difficult to walk on the ground and survive on a grass diet.
If all species were built the same and depended on the same food and methods of acquiring that food, habitats would quickly fail -- there simply wouldn't be enough food to last over time. Species already compete for resources. Without diversity, competition would be fierce. Less successful individuals have to leave, die, or have the ability to adapt their eating and survival behavior.
Animals with a versatile body design and life habits can adapt their behavior to survive. Please note that adapting behavior is different from physical adaptation. Adaptations are physical changes that happen over generations. Physical adaptations cannot, at will, be changed. Adaptations such as the shape of a skull, location and shape of a eyes and mouth, capabilities of claws and paws or methods of locomotion, etc., are adaptations that help determine how well individuals and ultimately, a species in a certain habitat can survive. As individuals within a population of a species have the ability to cope with a habitat, they are more likely to survive and have young with similar characteristics. Animals capable of taking advantage of broader food, shelter or water opportunities through their body adaptations and ability to alter their behavior are called generalists. Generalists have a better chance for survival. Many rare species are specialists. Specialists depend on very specific habitat needs or behavior. When the habitat is altered, it may be beyond their ability to survive.
How many individuals a habitat can support is referred to as carrying capacity. Having a variety of species with varying eating habits helps maintain a larger, natural carrying capacity. The interdependence of species defines the biotic part of an ecosystem. Within an ecosystem are interdependent food webs, with species of varying physical features, ability to obtain food, and sources of food. Each species has a role in the ecosystem of eating, being eaten, decaying and contributing in some way to the ecosystem. This role is called it's niche.
Skulls offer clues about whether an animal is best suited for being a predator or a prey. Keen predators have eyes sockets toward the front of their skulls offering the animal the ability to use 3-D to estimate distance and more precisely pounce on prey. Eye sockets on the sides of skulls are best suited to prey who must keep a vigilant watch all around to spot an potential predator.
Scientists often use teeth shape and arrangement, called dentition, as one of the keys to determine where a species belongs in terms of genus and family.
This excerpt from the Association of Fish and Wildlife Agencies Core Concepts offers more ecological foundation for this month's feature.
The health and well-being of fish, wildlife, and humans depend on the quality of their environment.
- All living things depend on habitat that includes adequate and suitably arranged food, water, shelter, and space.
- Fish and wildlife numbers and species compositions are constantly changing based on a variety of natural and human-caused conditions.
- Loss and degradation of habitat are the greatest problems facing fish and wildlife; therefore, enhancing and protecting habitat is critical to managing and conserving them.
- Human changes to the landscape alter fish and wildlife habitat, changing the amount and type available.
- Natural events alter the landscape, changing the amount and type of fish and wildlife habitats available. The effects of these events can be exacerbated by human changes to the landscape.
- Fragmentation of habitats alters fish and wildlife distribution, movement, and composition.
- The carrying capacity of an area determines the size of the population that can exist or will be tolerated there.
- Biological carrying capacity is an equilibrium between the availability of habitat and the number of animals of a given species the habitat can support over time.
- Cultural carrying capacity is the number and type of a given species that people will tolerate over time.
- Carrying capacity is dynamic and can change from season to season and from year to year.
- Regulated hunting, fishing, and trapping are important tools for preventing populations of certain species from exceeding the carrying capacity of their habitat.
- Living things tend to reproduce in numbers greater than their habitat can support. The populations are limited by factors such as quantity and quality of food, water, shelter, and space. Other limiting factors may include disease, predation, and climatic conditions.
- When a population becomes too large it may damage or destroy its habitat as well as habitat for many other species.
- When a population exceeds the carrying capacity for an area, individuals of that population must out-compete others, emigrate, or die.
- Fish and wildlife are present in nearly all areas of the earth. Each ecosystem has characteristic species.
- Climate, topography, and habitats influence species diversity.
- All living things are connected to each other and their environment.
- Plants and animals in ecological systems live in a web of interdependence in which each species contributes to the function of the overall system.
- Energy from the sun is captured by plants and enters the animal world primarily through animals that eat plants.
- Interactions between different fish and wildlife populations include competition, predation, and symbiosis.
- Each species occupies a niche within its environment.
- Ecological succession is a process involving continuous replacement of one community by another.
- As succession occurs fish and wildlife found in that community will change.
- Natural events and human activities affect the rate and direction of succession.
- Species differ in their ability to adapt.
- a. Fish and wildlife are adapted to their environment in ways that enable them to compete and survive.
- b. The more adaptable a species is, the more likely it is to thrive.
- c. Most species that are endangered or threatened in North America became so as a result of natural or human-caused changes in their habitat and their inability to adapt or adjust to such changes.
- Conserving biodiversity is important.
- Isolated ecosystems and populations are more vulnerable to environmental change than well connected ecosystems.
- Native species are important to the stability of an ecosystem.
- Exotic/non-native species introduced into a community can change the dynamics of that community.
- Reintroduction of fish or wildlife into its former range may be possible if conditions such as suitable habitat and social acceptance exist.
- Many species are indicators of environmental health.