Study Guide: Quiz 3 Ecology

Transcription

1 Study Guide: Quiz 3 Ecology 1. The Origins of Ecology: Linnaeus, Darwin, Haeckel & Richards Linnaeus wrote poem regarding ecology, stating that all of nature was created for some end and how each part of nature had its significance Darwin s theory of evolution applies to ecology: plants out-compete each other (natural selection), and thus, certain plant species increase in numbers relative to other species Haeckel wrote a book on ecology (Generelle Morphologie der Organismen) and provided the first definition of the term as follows: By ecology, we mean the body of knowledge concerning the economy of nature the total relations of the animal to both its inorganic and organic environment In a word, all the complex relationships referred to as the struggle for existence Ellen Swallow Richards 1 st woman to graduate in chemistry at MIT; interested in environment; introduced word ecology to the US 2. The biosphere and the major biomes (if someone showed you a picture of one of the biomes we discussed, you should know its name and a general understanding of its climate, e.g. hot & dry, cool & moist etc.) Biomes are the largest definable regional ecosystems on the Earth that have developed under specific soil and climatic conditions and are characterized by distinct types of vegetation, animals and microbes Terrestrial Biomes Tropical forest = warm, variable rainfall, poor soil Savanna = warm year-round, variable rainfall (average 30-50cm/yr), grassland w/scattered trees, poor soil

2 Desert = very dry, low/unpredictable rainfall Chaparral = cool ocean currents, mild/rainy winters and hot/dry summers, dense/spiny shrubs w/tough evergreen leaves Temperate grassland = mostly treeless, found in regions of cold winter temps, precipitation = 25-75cm/yr average, periodic severe droughts

3 Temperate broadleaf forests = sufficient moisture to support large trees, deciduous trees, very cold in winter and very hot in summer, high precipitation (average cm) Taiga = Coniferous forest = long/cold winters, short/wet summers, most precipitation = snow Tundra = extremely cold, little light for fall/winter, permafrost, little precipitation Polar Ice = extremely cold year-round, precipitation very low

4 Aquatic Biomes Freshwater 1. Lakes/ponds 2. Streams/Rivers 3. Wetlands Marine 1. Oceans 2. Coral reefs 3. Estuaries 3. A general understanding of the chemical transformations of oxygen, carbon, and nitrogen by life in the biosphere and the biospheric cycles that have sustained life on Earth for 3.8 billion years (see article on the Biosphere). Biosphere (life) interacts with hydrosphere (water), lithosphere (rocks) and atmosphere (air) 1 of the major effects of the biosphere has been the influence on the atmosphere Oxygen Currently, O 2 production by biosphere = O 2 consumption by respiration Photosynthesis is responsible for 0.002% of this total Cyanobacteria are crucial to replenishing atmospheric O 2 Carbon Cyanobacteria are responsible for 50% of all photosynthetic production (Net Primary Productivity NPP) in Earth s oceans, meaning 25 billion tons of carbon per year Phytoplankton are responsible for the other 50% of the NPP Terrestrial environments produce the same amount of carbon each year as the oceans Photosynthesizing bacteria and plants extract over 100 billion tons of carbon as CO 2 from the atmosphere Respiration and decomposition of organic matter by microorganisms returns CO 2 to the atmosphere Nitrogen Rhizobium bacteria, which grow in small nodules on the roots of legumes, and cyanobacteria break the triple bond in the atmospheric N 2 and convert it to NH 3 Organisms excrete some of the nitrogen they use back into the environment as NH 3 The remaining nitrogen trapped in their proteins and nucleic acids is liberated by bacterial decomposition when they die The nitrogen cycle is completed when other bacteria obtain energy by oxidizing NH 3 to NO 3 - and NO 3 - to N 2

5 4. Whittaker diagram 5. Climate diagram See above diagram 6. Gaia and Daisy World The Gaia hypothesis asserts that organisms and their environment evolve together since species that leave the most offspring inhabit a particular environment, and these organisms will sustain and modify the environment in which they live; thus, the Earth s environment is homeostatic an environment optimal for life is maintained In Daisy World there were black and white daisies Black daisies absorbed more light, obtaining a high temperature more quickly White daisies reflected more light, taking longer to obtain a high temperature There was a certain optimal temperature for daisies, but the black and white daisies obtained that temperature at different rates Thus, temperature and the daisy population essentially evolved together, much as the Gaia hypothesis asserts an ecological system will work 7. Origin of major patterns in atmospheric circulation Hadley cells = circulation patterns that dominate the tropical atmosphere In Hadley cells, air warms, picks up moisture and rises near the equator Cooled, dried air descends at about 30 o North of the equator Once again, air warms, picks up moisture at about 60 o North of the equator At the north pole, once again, cooled, dried air descends

6 Coriolis Effect = Winds in the Northern hemisphere are deflected to the right of their direction of travel, and winds in the southern hemisphere are deflected to the left 8. The mechanism behind seasonal change Seasons of year result from permanent tilt of planet on its axis as it orbits the sun Globe s position relative to sun changes through the year For instance, the Northern Hemisphere is tipped most toward sun in June (hence June = summer for America) B/c the Northern Hemisphere is tipped most toward sun in June, at this time, the sun faces Earth at a more direct angle, and there is increased intensity from the sun, resulting in long, summer days However, in June, the Southern Hemisphere has short, winter days The Southern Hemisphere is most tipped towards the sun in December 9. Idea of positive and negative feedback within a system and how such feedback can regulate the system around a long term average. Positive Feedback A type of control in which a change triggers mechanisms that amplify that change Negative Feedback A primary mechanism of homeostasis, whereby a change in a physiological variable triggers a response that counter-acts the initial change The biotic and abiotic factors affecting abundance of organisms can regulate the system through positive or negative feedback 10. The concept of the Balance of Nature and biotic vs. abiotic influences on abundance The Balance of Nature is an idea suggesting that populations in nature are regulated around some average density, neither increasing without limits nor decreasing to extinction This view depends on the idea that biological factors (such as food and predators) were the crucial determinants of population abundance Thus, supporters of this view believe in density-dependent regulation So, for example, if there were many individuals, the food supply would be over-eaten, resulting in fewer individuals; now, with fewer individuals, there is more than enough food for everyone, and birth rates exceed death rates, resulting in the population level rising again In summary: Many individuals Few individuals Many individuals Thus, the population is essentially being regulated such that there is an average number of individuals over time We now know that it is a combination of density-dependent and density-independent factors that are important in determining population abundances through time Abundance is affected by the following biotic/abiotic factors: Weather (abiotic) Food (biotic) Predators (biotic) Parasites (biotic) Disease (biotic/abiotic)

7 Competitors (biotic) Habitat (biotic) 11. Complex systems & their general properties Complex system = large # of connected, interacting components that affect each other and change throughout time Properties 1. Nonlinear Effects Effects of one variable on another aren t constant (small changes can have big effects); graph is non-linear - may be exponential, etc. 2. Multiple Causation When several variables influence the behavior or magnitude of another part of the system 3. Nonproximate Cause and effect removed in time and space 4. Sensitivity to initial conditions Butterfly effect ; the trajectories of the two systems will diverge exponentially through time; the small difference between 2 complex systems is amplified as time passes 5. Emergent properties Systems level phenomena that arise from the collective interaction of the system s separate components; usually not predictable from detailed knowledge of system s individual components Examples Human brain many different parts Social interactions between high school students large network of connections Internet another large network of connections; many components 12. The definition of an ecological population A group of individuals of the same species living together in the same place at the same time 13. The idea of exponential growth and examples Growth under conditions of unlimited resources All populations are capable of exponential growth 14. Doubling time If t = doubling time and r = rate, then t = 0.7/r Ex: If population grows at 10%/yr (r = 0.1), then doubling time (t) = 0.7/0.1 = 7 years 15. The idea of limited population growth, the logistic equation, & carrying capacity Population growth can be limited by biotic (food, habitat, interactions ex: predation, competition, parasitism, disease) and abiotic (light, nutrients, water, temperature, ph) factors The logistic equation is the simplest model of limited growth In the equation, K = carrying capacity = maximum population that can be sustained in a given habitat at a given time Logistic equation: dn/dt = rn[1 (N / K)] 16. The concept of r & K selection with examples for each r selection

8 Many offspring produced Only 1 reproduction in lifetime (thus many offspring produced that 1 time) No parental care Small eggs/offspring (less chance of being found) High mortality rate Short lifespan Short maturation time (greater chance of growing up to reproduce) Limited homeostatic capability Examples: Dandelions, house flies, house mice K selection Few offspring produced Several reproductions in lifetime Extensive parental care Large eggs/offspring Low mortality rate Long lifespan Long maturation time Often extensive homeostatic capability Examples: Blue whales, horses, coconut trees 17. How populations are regulated by density dependent feedback Density-dependent factors = limiting factors whose intensity is related to population density; factors that regulate population abundance around some mean value by acting more strongly to inhibit growth at high numbers and less strongly at low numbers Ex: Intraspecific competition = competition between individuals of same species for limited resources; as there are more and more individuals competing for a limited food supply, birth rates may decline as individuals have less energy available for reproduction (due to less food for more individuals resulting in less food per individual) 18. Fluctuations in resources & other environmental factors (e.g. weather) and their effects on births, deaths, & population dynamics Fluctuations in resources/environmental factors alter the maximum carrying capacity A good change (ex: beneficial weather) increases carrying capacity; in other words, the birth and death rates become equal at a greater population size A negative change (ex: harmful weather) decreases carrying capacity; in other words, the birth and death rates become equal at a lower population size 19. The Sun s radiant energy comes from the following sources: Fusion The sun s core reaches very high temperatures At such high temperatures, 4 hydrogens are converted into 1 helium The helium has slightly less mass than the 4 hydrogens That missing mass was simply converted to energy (E = mc 2 ) Electromagnetic radiation Radiation emitted by the sun

9 ½ of this radiation is in the visible part of the electromagnetic spectrum The other ½ of the radiation is mostly in the near-infrared and ultraviolet part of the spectrum Inverse square law The intensity of the sun s radiation decreases as the distance from the sun increases Mathematically, this idea is stated as: I α 1/r 2 Albedo, absorption and the radiant energy that is ultimately available for photosynthesis on the Earth s surface Albedo = proportion of solar radiation reflected by a surface Average albedo for earth = 30% Fresh asphalt has low albedo (0.04) Fresh snow has high albedo (0.85) 51% of the incoming solar energy is absorbed by the land and oceans 16% absorbed by atmosphere 3% absorbed by clouds Thus a total of 70% (51% + 16% + 3%) of the incoming solar energy is absorbed This 70% of the incoming solar energy is available for photosynthesis Notice that 100% of the sun s radiant energy is reflected (30%) or absorbed (70%) by Earth Earth s orbit around Sun & the origin of the seasons Seasons of year result from permanent tilt of planet on its axis as it orbits the sun (allowing Earth to receive radiant energy from sun and reflect or absorb the energy) 20. Stable limit cycles, period doubling, and chaos in population dynamics as exhibited by the discrete logistic model of population growth Discrete logistic model of population growth = model for population where births and deaths don t occur continuously but, rather, only at certain times; population abundance for generation n + 1 can be calculated based on various rates of increase (r) in the previous population, n Initially, there will be a stable point (graph is horizontal) As r increases, the period (# of generations it takes population to return to original value) will start doubling Eventually, smaller and smaller increases in r will cause the period to double As r increases further yet, chaos will occur eventually The chaos results from populations with high r overshooting K (in other words, growth rate exceeds carrying capacity) and nonlinearity of logistic growth Strong density dependence causes rapid decline in abundance, followed by overshoot, another decline, etc. (Few individuals Many individuals Few individuals Many individuals; See Concept 10: Balance of Nature above for better explanation) 21. Basic definition of competition Any use or defense of a limited resource by members of 1 population that reduces the availability of that resource to other members of the same or different species 22. The Gause competitive exclusion principle

10 2 species competing for the same resources cannot coexist if other ecological factors are constant When one species has even the slightest advantage or edge over another, then the one with the advantage will dominate in the long term 1 of the 2 competitors will always overcome the other, leading to either the extinction of this competitor or an evolutionary or behavioral shift towards a different ecological niche If 2 or more species live in stable association, they must possess different ecological niches This idea is a central principle to ecology 23. The idea of the ecological niche (brief definition) The set of environmental conditions under which an organism can survive and reproduce, including the resources it exploits for food and the range of physical conditions it can tolerate The niche of any species is multidimensional for example, 1 environmental condition (dimension) that might be taken into consideration for the niche is light intensity, another is the nutrients available, and another is the ph of the environment