Topic 8 Study Guide PDF PDF

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Dr. Auerbach, weekly study guide...

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Topic 8 Study Guide: Organismal and Population Ecology Big Idea: All living species have evolved heritable adaptations for living in their abiotic and biotic environments. Population ecology studies the distribution and abundance of organisms within a population, and how both change over time. 1. Read your text book and complete the Study Guide: Chapter 49: An Introduction to Ecology Chapter 51: Population Ecology The Big Picture: Ecology (follows Chapter 54) 2. Practice: Do the practice activities in MasteringBiology before class, (see due date on schedule). 3. Prepare: Come to class with at least one question to propose for class discussion. After you complete this Study Guide you should be able to: • Give examples of questions that you could ask at each level of ecological study. • Draw a niche model to show the abiotic tolerance of a species. • Explain how species distributions are affected by abiotic and biotic factors, past and present. • Compare which abiotic variables are most important in terrestrial and aquatic ecosystems. • Explain how to use an appropriate sampling method to measure population size. • Compare survivorship and fecundity. • Compare exponential population growth and logistic population growth. • Draw a graph of the human population growth curve and explain its shape. Introduction to Ecology 1. Define ecology. 2. It helps to think about ecology at different levels of organization. Level

Definitions

Example of a specific research question you could ask at this level, such as “What are the predators of blue crabs?”

Organismal ecology

Adaptation: Any heritable trait that increases the fitness of an individual with that trait, compared with individuals without that trait, in a particular environment

What prey do lions eat?

Population ecology

Population: A group of individuals of the same species that lives in the same area at the same time

How has the shark population off the coast of Ocean City changed over time?

Community ecology

Community: All of the populations of different species that interact with each other in a certain area

How do dolphins and sharks interact in the wild?

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Ecosystem ecology

Ecosystem: All the organisms that live in a geographic area, together with the abiotic components that affect or exchange materials with the organisms; a biological community and its physical environment

How does decomposition benefit organisms in an ecosystem?

Global ecology

Biosphere: The thin zone surrounding Earth where all life exists; the sum of all terrestrial and aquatic ecosystems

How has climate change affected animals in the ocean?

3. Palm trees don't live on Assateague and tigers don't live in Salisbury! Give examples of how abiotic and biotic factors in the present and past affect the distribution and abundance of organisms. Abiotic factors

Biotic factors

Present

Temperature: Organisms can only tolerate certain temps in order to survive

Access to pollinators: This allows plant species to have a wider distribution and more individuals

Past

Continental drift: Splitting of Pangaea affected the distribution and location of organisms

Animals that lived in the past interacted with each other, but most of them have disappeared

4. Sketch a niche model comparing the range of temperatures that can be tolerated by coconut palms and açai palms (see Figure 49.1). • • •

Which has a higher average heat tolerance? Acai palm Which has a larger range of temperature tolerance? Coconut palm Predict what would happen if you planted an açai palm in the uplands of Costa Rica where the average temperature is 15°C. It would die because 15 degrees C is below its tolerated temperatures

Climate Basics You will not be tested on the nuances of Hadley cells or the Coriolis effect in this course. However, you should understand the basics about climate patterns so that you can make sense of the distribution and abundance of organisms on Earth.

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5. Why are the tropics warm and the poles cold? The tropics are located at the equator so they get the most direct sunlight, while sunlight hits the poles at a low angle so they receive less energy. 6. Why are the tropics wet? Hadley cells: warm air rises and cools over the tropics, which then allows precipitation. 7. What causes seasonality in weather at high latitudes, such as in Maryland? Earth’s orbit and tilt. 8. What regional effects do mountains have on climate? Temperature decreases as elevation increases. 9. What regional effects do oceans have on climate? (Why is Ocean City cooler than Salisbury in the summer, and warmer than Salisbury in the winter?) Water has a high specific heat, meaning it has a large capacity for storing heat. So, it absorbs heat during the summer and releases it during the winter.

Terrestrial and Aquatic biomes 10. What is a biome? Note that the Sonoran Desert and Sahara Desert are different ecosystems (different plant and animal species live there) but they are both in the desert biome. A large terrestrial or aquatic region characterized by distinct abiotic characteristics and dominant types of vegetation. 11. Building on your knowledge of photosynthesis: What is net primary productivity (NPP)? NPP is the total amount of biomass generated by the fixation of carbon per year minus the amount that is oxidized during cellular respiration.

12. Review: Why do all heterotrophs like us depend on autotrophs for life? That is, what are the two ways that we use the organic molecules made by photosynthesizers to stay alive? One way that we depend on autotrophs is to produce oxygen so that we can breathe. Also, we need to eat them so we can get energy.

13. In which natural biome does Delmarva occur (see Figure 49.9)? Temperate forest 14. Which anthropogenic biomes occur on Delmarva (see Figure 49.10 and incorporate your personal observations)? Cities/suburbs, cropland 15. Food for thought: If all the people on Delmarva decided to move to Baltimore for a century, what would the landscape of Delmarva look like when they moved back? The landscape would be wildlands 16. Complete the chart using information in Section 49.4 and 49.5.

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Key abiotic factors defining these biomes

Terrestrial biomes

Aquatic biomes

Temperature Moisture Sunlight Wind

List the featured biomes (see Tables 49.3 ad 49.4) Arctic tundra, boreal forest, temperate forest, temperate grassland, desert and dry shrubland, tropical wet forest

Salinity Water depth Water flow Nutrient availability

Lakes and ponds Freshwater wetlands Streams Estuaries Oceans

Population Ecology Sampling Methods 1. If you were asked to measure the population size of açai palm trees in coastal Brazil, would you count every tree? No. If you were asked to measure the population size of toucans, would you count every toucan? No. In most biological research, you must make inferences based on samples. Type of organism

Examples

Immobile (or mostly immobile) organisms

trees, kelp, dandelions,

Counting individuals that occur along

mushrooms, barnacles

transects or quadrants

Mobile organisms lizards, rabbits, butterflies, fishes,

Example of sampling method you could use to measure abundance

Mark-recapture

snakes 2. Suppose you trap 255 stickleback fish in a lake and mark them by clipping the first spine of their dorsal fins. One month later you recapture a total of 162 individuals, 78 of them marked. Estimate the total population size (see Quantitative Methods 51.1). Show your work. Total pop size = 467

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List three of the many assumptions you are making when you use the mark-recapture method. •

Individuals are not moving in and out of the study area

•

Individuals mix between captures

•

No bias exists regarding which individuals are caught in each recapture

Demography and Life History 3. The number of individuals in a population depends on what four processes? Birth, death, immigration, emigration 4. What is survivorship? Define and give an example. On average, the proportion of offspring that survive to a particular age. For example, the Z. vivipara survivorship from birth to age 1 was 0.424 in the Netherlands population (that is, about 42 percent survived to age 1 and about 58 percent died). 5. What is fecundity? Define and give an example. The average number of female offspring produced by a single female in the course of her lifetime. Older female lizards have a higher age-specific fecundity than younger females. 6. Draw a model of a life-history continuum showing the relationship between survivorship and fecundity. Why isn’t it possible for an individual to have both high fecundity and high survivorship?

7. Review/Food for thought: Recall from the Cell Respiration and Photosynthesis topics that you eat food for two main reasons: as a source of chemical energy to run your metabolism and as a source of organic molecules to build your biomass (or the biomass of your gametes or offspring). Give an example of how there is a fitness trade-off in how you can use your food. (Hint: Use the evolutionary meaning of fitness; see Topic 1). Humans have a high survival rate but low fecundity. Because humans devote a large amount of energy to raising offspring because it takes us a long time to develop. So, we cannot have as high an amount of offspring.

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Population growth curves 8. Compare exponential and logistic population growth. Exponential Growth

Logistic Growth

Draw a graph to show the shape of this growth curve. (Don’t forget to label your axes.) Label the carrying capacity where appropriate.

When/where would you find this type of population growth in nature?

Occurs when resources are

Occurs when resources have

unlimited

become limited

Colonization of a new habitat Recovery after a disaster Is density-dependent or densityindependent growth occurring?

Density independent

Density dependent

9. What density-dependent factors limit population size? (See Table 51.2) Density-dependent factor

Example of population experiencing this factor

Competition for resources

Dense tree saplings compete for limited light, water, and nutrients

Disease and parasitism

Pigs in dense confinement are prone to illness

Predation

Hare density influences lynx predation rates

Toxic wastes

Densities of fruit fly larvae are limited by ammonia buildup from their feces

Social behavior

Blue crab cannibalism increases with density

10. Define carrying capacity. Can the carrying capacity be surpassed? Explain. (See Figure 51.9)

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Carrying capacity is the number of living organisms that a region can support without environmental degradation. The carrying capacity can be surpassed, however once it is surpassed the population will undergo a harsh decline because they do not have sufficient resources. 11. Draw a graph of human population growth over the last 2000 years. Include units on both axes to help you plot the actual data (See Fig. 51.15). Does this curve resemble exponential or logistic growth? Exponential growth

12. Now extend your y-axis and population growth curve in your graph above to show how you predict the human population will look in year 2100 (that is, combine your prediction from Figure 51.16 with your curve from 51.15). Explain your reasoning. The population will decrease because the carrying capacity for humans has been surpassed.

13. Food for thought: Which density-dependent factors do you think are most relevant to predicting human population size over the next century? I think competition for resources will be the most relevant to predicting human population size. We can already see competition issues today, people all over the world are starving and have no access to fresh water. People in the US have a huge surplus of food while in some countries, children starve to death because they have none. This problem could affect the future human population.

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