CHAPTER 5 Engage Your Environment: Species Richness Does species richness differ
ID: 180910 • Letter: C
Question
CHAPTER 5 Engage Your Environment: Species Richness Does species richness differ in areas of human disturbance? In this activity you’ ll survey two habitats, one disturbed and one undisturbed, and you will compare the species richness of both. Does species richness differ in areas of human disturbance? Learning Objectives You will: Understand the concept of species richness. Compare species richness in both natural and disturbed habitats. Resources Two sampling habitats, one natural and one disturbed, on your campus or in your community. Each of these habitats should be approximately ¼ acre in size. Introduction The number of species present in a defined area is known as species richness. It varies greatly among habitats and can be influenced by many factors, including altitude, latitude, the availability of water, and the degree of disturbance. Environmental scientists use species richness as one indicator of biological diversity that gauges ecosystem health and function. Determining species richness in two habitats in your community will allow you to evaluate the variety of plant species present and the level to which disturbance influences the number of species. Background Questions A1. Why is species richness a valuable indicator of ecosystem health and function? A2. How might new species arrive in a habitat? A3. Why might a species “decide” to colonize one particular habitat over another? A4. How do humans influence the colonization of species into new habitats? Methods B1. Determine the number of plant species present in two habitats in your community. Choose two habitats of approximately the same size but differing in the levels of human disturbance. Each habitat should be approximately ¼ acre in size. The “natural” habitat should be as undisturbed by humans as possible. This habitat may be a wooded area, a park, or open space. The “disturbed” habitat should exhibit some level of human disturbance, and could be located at the edge of a parking lot, near a building, or beside a cleared lot. In the appropriate column of Results Table 1 list the names of all plant species present in the natural and disturbed habitats. If you do not know the name of a species, name it yourself (for example, Plant species 1, Tree species 1) and make note of key characteristics (for example, size, leaf shape, flower color, the number of leaves, or type of stem, such as woody, green stem, or vine). Be consistent in naming and describing your species to avoid counting the same species multiple times. Results Table 1 Plant Species Richness Species Name and/or Description Natural Habitat Disturbed Habitat Total Number of Species: Total Number of Species: Follow-up C1. Describe the size and basic features of both the natural habitat and the disturbed habitat. C2. How many species were present in the natural habitat? How many were present in the disturbed habitat? What factors do you think account for this difference? C3. What differences, if any, were present in the types of species found in disturbed and undisturbed areas? C4. Propose a hypothesis to explain how disturbance affected species richness in these particular habitats.
Explanation / Answer
Background question answers:
A1: Species richness is a valuable indicator of health and function. It is important for an healthy ecosystem to have stability and that can only happen with the abundance of species. If there are enough number of individuals from one species that can compensate for the other. For eg: if there's a sudden extinction of one species, because of the abundance of the other, , it can compensate for the decreased abundance of the other species.
A2: New species might arrive in a habitat by immigration- i.e. the new species colonizing a habitat. This can be given by a theory proposed by Robert MacArthur and E.O. Wilson, the equilibrium theory of Island Biography; where islands represent habitats. This theory proposes that the number of species on any island reflects a balance between the rate at which the new species colonize (immigration) and the rate at which populations of established species become extinct (extinction).
A3: A species might decide to colonize over another species in case where there is extinction of the pre existing species, confirming the theory of survival of the fittest.
A4: Humans influence the colonization of species into new habitats by causing a disturbance in the species diversity and by altering the resource availability, thus removing the organisms from that habitat. This also influences the species co-existence and maintenance of biodiversity.
The rest of the questions C1-C4 cannot be answered as they are based on field results.