Age Distribution Graph

Transcription

1 ECOLOGY Student Packet SUMMARY COMMUNITIES ARE COMPOSED OF POPULATIONS THAT INTERACT IN COMPLEX WAYS Competition, predation, parasitism, mutualism, and commensalism affect population dynamics. Reproduction without constraints results in the exponential growth of a population. As limits to growth are imposed by density-dependent and density-independent factors, a logistic growth model follows. Density-dependent factors include competition for resources, territoriality, disease, predation, accumulation of wastes, etc. Density-independent factors include natural disasters, temperature, amount of sunlight, etc. Demographics data with age distributions and fecundity (capacity of offspring production) can be used to study human population growth. Age Distribution Graph INTERACTIONS AMONG LIVING SYSTEMS AND THEIR ENVIRONMENT RESULT IN MATTER AND ENERGY MOVEMENT Energy flows but matter is cycled. Changes in climate influence primary productivity. Food webs and food chains are dependent on primary productivity. Many adaptations of organisms are related to obtaining and using energy and matter in a particular environment. Due to the laws of thermodynamics, energy cannot be created or destroyed. However, with each energy transformation, some energy becomes unusable. The unusable energy is usually in the form of heat and causes an increase in entropy. 1

2 DISTRIBUTIONS OF SPECIES AND ECOSYSTEMS CHANGE OVER TIME Environmental catastrophes, geological and meteorological events and increased human activities affect species distribution and distribution of local and global ecosystems. Human impact often reduces population size of the affected species, destroys habitats and in some cases causes extinction of species. Examples include: logging, slash and burn agriculture, urbanization, monocropping, infrastructure development, global climate change and introduction of new diseases/species. Introduced species can exploit a new niche free of predators or competitors. Ecosystems with fewer components and little diversity are often less resilient to changes in the environment. Keystone species, producers, abiotic factors and biotic factors contribute to maintaining the diversity of an ecosystem. When keystone species are removed from an ecosystem, the ecosystem often collapses. ALL BIOLOGICAL SYSTEMS FROM CELLS TO ECOSYSTEMS ARE AFFECTED BY BIOTIC AND ABIOTIC INTERACTIONS The stability of cells, organisms, populations, communities and ecosystems is affected by interactions with biotic and abiotic factors such as food and water availability, temperature, and population density. ORGANISMS RESPOND TO CHANGES IN THEIR EXTERNAL ENVIRONMENTS Organisms respond to changes in their environment through behavioral and physiological mechanisms. Animals use visual, audible, tactile, electrical and chemical signals to indicated dominance, find food, establish territory and ensure reproductive success. Natural selection favors innate and learned behaviors that increase survival and reproductive fitness. Innate behaviors are behaviors that are inherited. Learning occurs through interactions with the environment and other organisms. Cooperative behavior tends to increase the fitness of the individual and the survival of the population. 2

3 MULTIPLE CHOICE QUESTIONS 1. Interdependence in nature is illustrated by the transfer of energy through trophic levels. The diagram below depicts the transfer of energy in a food web of a lake located in Alaska. If the cells in the dead terrestrial plant material that washed into the lake contained a commercially produced toxin, what would be the likely effect of this toxin on this food web? a. Toxins pose greater risk to lake trout than to larvae and snails because lake trout is a top-level predator. b. The producers would be negatively affected the most because their biomass is higher than the biomass of primary consumers. c. Larvae of aquatic insects would be the most impacted because they directly feed on the contaminated plant material. d. The sculpin population would not be greatly affected because it is smaller than populations of primary consumers. 2. Decomposers play a critical role in recycling chemical elements back to primary consumers and net primary production (NPP) is an important concept when describing energy availability in ecosystems. If you applied a fungicide to a cornfield, what would you expect to happen to the rate of decomposition and net primary production? a. Both decomposition rate and NPP would increase. b. Both decomposition rate and NPP would decrease. c. Neither would change. d. Decomposition rate would decrease and NPP would increase. 3. If there are 100,000 kilojoules (kj) of energy available at the producer level due to photosynthesis, which of the following statements correctly describes the flow of energy in the system? a. The grasshoppers have a maximum of 100,000 kj of energy. b. The grasshoppers have approximately 1,000 kj of energy. c. Shrews have approximately 1,000 kj of energy. d. Owls have approximately 10,000 kj of energy. 3

4 4. Which of the following strategies would most rapidly increase the genetic diversity of a population in an extinction vortex? a. Capture all remaining individuals in the population for captive breeding followed by reintroduction to the wild. b. Establish a reserve that protects the population s habitat. c. Introduce new individuals transported from other populations of the same species. d. Sterilize the least fit individuals in the population. 5. The graph below shows changes in population sizes of three species of cold sea penguins: adelie, chinstrap, and gentoo penguins. Adelie penguins need ice as a platform to feed on krill while chinstrap and gentoo penguins prefer to live in areas with less ice. Which of the following explanations is the least likely reason for the trends shown in the graph? a. Numbers of adelie penguins are decreasing due to global climate change. b. Populations of chinstrap and gentoo penguins are increasing because they are introduced species free of predators and competitors. c. Populations of adelie penguins are decreasing due to habitat fragmentation. d. As the climate of the arctic ecosystem changes, the distribution of penguin species changes as well. 4

5 6. The graph shows changes in the number of species in an aquatic ecosystem when an aquatic organism Pisaster is present vs. when it is absent. Based on the data, Pisaster is most likely a(n) a. dominant species. b. invasive species. c. overharvested species. d. keystone species. 7. Scientists conducted an experiment to determine which nutrient(s) limit(s) aquatic production in the Sargasso Sea. They added a known amount of the radioactive isotope C-14 to a water sample. Algae then incorporated C- 14 in their organic molecules along with C-12, which is widespread in water. Based on the data, what is/are the limiting nutrient(s) in the Sargasso Sea? a. Nitrogen b. Iron c. Nitrogen and phosphorus d. Nitrogen, phosphorus, and iron 5

6 8. Researchers Christopher Ramnanan and Kenneth Storey studied estivation in the land snail Otala lactea. Estivation is a condition characterized by inactivity and a lowered metabolic rate in response to high temperatures and arid environment. The scientists measured the amount of ATP used by the membrane pump Na + /K + -ATPase (recorded as S 0.5 ATP) in foot muscles (graph A) and in hepatopancreas (graph B) as a function of temperature. Which of the following is not supported by data from the experiment? a. Na + /K + -ATPase activity was significantly reduced in both foot muscle and hepatopancreas in O. lactea during estivation. b. As one of the largest consumers of cellular ATP, Na + /K + -ATPase can be used to determine the metabolic rate of organisms. c. There is no statistical difference in the activity of Na + /K + -ATPase between the estivated and active snails as indicated by the * in the graphs. d. Estivation in snails is triggered by environmental conditions. 9. Which of the following statements incorrectly describes how the communication among individuals within a population may increase the long-term success of the population? a. Innate behaviors may increase survival of organisms while learned behaviors generally do not improve survival outcomes. b. Predator warning by some members of a population increases the survival of the population. c. Living organisms have a variety of signal behaviors that produce changes in the behavior of other organisms and result in differential reproductive success. d. Organisms exchange information with each other in responses to internal changes and external cues. 6

7 MATH GRID IN 1. A population of fire ants in the Mobile-Tensaw River Delta exhibits a logistic growth pattern. The carrying capacity of the ant mound is 15,000 ants. The maximum per capita growth rate, r max, is 0.9 fire ants per month. Calculate the maximum population growth rate for this population if the maximum occurs when N = K/15. Give your answer to the nearest whole number. 2. The biomass of a deciduous forest is 50% carbon. Additionally, the biomass increases annually at a rate of 2.7 x 10 5 kg/hectare. Calculate the mass of carbon accumulated and stored in 3 hectares of this forest in one year. Give your answer to the nearest hundredth of 10 5 kg. 7

8 SHORT FREE RESPONSE QUESTIONS 1. Bacteria play central biological roles. They may act as parasites, mutualistic symbionts, decomposers. Select TWO of the ecological roles above. For each one you choose, describe how bacteria carry out the role and discuss its ecological importance. 2. In many ways, all organisms in a food web can be said to be solar-powered. The producer level of the food web is responsible for the transformation of the solar energy into a form that can be used by other living organisms. Discuss the flow of energy from producers through top carnivores in a food web in terms of the laws of thermodynamics. 8

9 LONG FREE RESPONSE QUESTION Ecological succession describes the pattern of changes in communities over time. The graph below shows changes in plant diversity following the abandonment of an agricultural field in a temperate biome. a. Discuss the differences in plant diversity shown in the graph and explain how the changes affect the animal species composition between years 0 and 120. b. Identify TWO biotic and TWO abiotic factors and discuss how each could influence the pattern of ecological succession. c. Design a controlled experiment to determine how the diversity of plant species in a newly abandoned field would be affected by large herbivores. 9

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