General Principles of Ecology

Biology 1 (E) Ecology General Principles of Ecology ● The biosphere consists of all of Earth’s organisms, plus the physical space we all inhabit o Includes inorganic chemicals like water, our nitrogen-rich atmosphere, and every living organism o Is crucial to our survival and well-being because human beings depend on the biosphere for food and raw materials o The biosphere is the integration of all the environments on Earth. ● Ecology: the scientific study of interactions between organisms and their environment o ● Helps us understand the natural world we live in The environment of an organism includes: o Biotic factors: other living organisms o Abiotic factors: nonliving Q1: List as many biotic and abiotic factors in this photograph as you can. Q2: Is the forest part of the biotic or abiotic environment? Q3: Is the river part of the biotic or abiotic environment? Climate and Weather ● Climate change: a large-scale and long-term alteration in Earth’s climate ● Climate: the prevailing weather of a region over relatively long periods of time (30 years or more) o ● Organisms are more strongly influenced by climate than by any other feature of their environment. Weather: short-term atmospheric conditions in a limited geographic area o Today’s temperature, precipitation, wind, humidity, and cloud cover Q1: Name 2 ways in which climate change affects the frequency and severity of floods. Q2: How has climate change caused a rise in sea level? Q3: Give an example of an environmental effect of climate change in your state or region. “Global Warming” and “Climate Change” Are Not Synonymous ● Global warming: a significant increase in the average surface temperature of Earth over decades or more o ● Caused by an increase in greenhouse gases that absorb heat that radiates from Earth’s surface and prevents it from escaping to space Greenhouse gases: o Carbon dioxide (CO2), water vapor (H2O), methane (CH4), and nitrous oxide (N2O) o Function much as the walls of a greenhouse or the windows of a car do: they let in sunlight and trap heat o Cause the greenhouse effect ● Atmospheric CO2 Levels Are Rising Rapidly o Human activities, such as the burning of fossil fuels, have released an excess of greenhouse gases into the atmosphere. o The infamous king of greenhouse gases: carbon dioxide (CO2) Q1: What measurements do the green circles represent? Q2: What measurements do the red circles represent? Q3: For approximately how many years has the Mauna Loa Observatory been recording CO2 levels? Q1: In what years were global temperatures the lowest? Q2: In what years were global temperatures the highest? Q3: What trend is apparent in this graph of actual global temperatures? The Carbon Cycle ● ● The global carbon cycle: the transfer of carbon within biotic communities and their physical abiotic surroundings Carbon is transferred between the biotic and abiotic through: o Photosynthesis: Sunlight, water, and CO2 to become sugar and O2. o Respiration: Take up O2 and release CO2 through metabolism o Combustion: the burning of carbon-rich materials, living or not Q1: What are 3 ways that carbon is released into the atmosphere? Q2: Are all the pathways you listed for question 1 affected by human activity? Q3: What are two biotic reservoirs of carbon? Carbon Sinks and Sources ● Carbon sink: a natural or artificial reservoir that absorbs more carbon than it releases ● Carbon source: a natural or artificial reservoir that releases more carbon than it absorbs Q1: How does a carbon source contribute to global warming? Q2: How does a carbon sink protect against global warming? Q3: How can trees act as both a source and a sink? The Hydrologic (Water) Cycle ● Hydrologic cycle: the circulation of water from the land to the sky and back again Q1: What is transpiration? Q2: Why is transpiration important to the water cycle? Q3: If there are fewer plants and therefore less transpiration in a given area, what will happen to the humidity or cloud cover in this area? How Big is Your Ecological Footprint? ● Ecological footprint: the area of the biosphere required to produce the resources and to absorb the waste produced by an individual or population Sustainable? ● An action or process is sustainable if it can be continued indefinitely without causing serious damage to the environment. ● Human impact on the biosphere is not sustainable at the moment, without continued action Your Ecological Footprint Depends on 4 Main Types of Resource Use ● 1. Carbon footprint: energy use ● 2. Food footprint: The land and energy and water it takes to grow what you eat and drink ● 3. Built-up land footprint: Includes the building infrastructure (from schools to malls) that supports your lifestyle ● 4. Goods-and-services footprint: Includes your use of everything from home appliances to paper products. Ecosystems ● Ecosystem: a group of communities interacting with one another in a physical environment o Where the biotic (living) world interacts with abiotic (nonliving) world o Defined by ways in which energy and nutrients are used by the biotic community o Ex: overfishing has decimated fish populations in Nova Scotia, affecting the entire ecosystem The Path of Energy in an Ecosystem ● Producers capture energy from the sun and transform it into fuel andergy. ○ Fuel energy is passed up the food chain as one organism eats another. ● An energy pyramid represents the amount of energy available to organisms. ● Each level of the pyramid corresponds to a step in a food chain and is called a trophic level. ● Example of an energy pyramid: ○ Phytoplankton are at the first trophic level ○ Zooplankton, larger, multicellular plankton that feed on phytoplankton, are the second trophic level ○ Small fish, such as the herring, are the third trophic level ○ Large fish, such as tuna, are the fourth trophic level Energy Cannot Be Recycled Within an Ecosystem ● At each trophic level, some energy captured by producers is lost as metabolic heat. ● Metabolic heat: the heat released as a by-product of chemical reactions within a cell ○ Organisms lose a lot of energy as metabolic heat ● Energy: ○ ○ ○ ○ ○ ○ ○ Only 10% at one trophic level is transferred to the next trophic level. The 90% not transferred is either: ■ 1. Not consumed. Example: When we eat an apple, we eat only a small part of the apple tree. ■ 2. Not taken up by the consumer’s body. Example: We cannot digest the cellulose contained in the apple. ■ 3. Lost as metabolic heat. Flows in only one direction through ecosystems because of this steady loss of heat Enters Earth’s ecosystems from the sun and leaves them as metabolic heat Captured by producers and eventually lost from the biotic world as heat Cannot be recycled within an ecosystem Travels up an energy pyramid, never down Q1: What percentage of the original 10,000 kilocalories is available to a shark that might eat the tuna in this figure? Q2: What trophic level and term would describe a predator of tuna? Q3: Give an example of a primary consumer in a terrestrial environment. Nutrients Are Constantly Cycled Between the Abiotic and Biotic Worlds ● Nutrients: chemical elements required by living organisms ○ Recycled and reused within and across ecosystems ○ Pass through the abiotic world ■ From rocks and mineral deposits into soil, water, and air ○ Pass to the biotic world ■ Via absorption by producers ○ Cycled among consumers once in the biotic world ● Earth gets a constant stream of light energy from the sun. ○ And, a constant and finite pool of nutrients cycles through the land, water, and air. Q1: Which organisms are the producers in this ecosystem? Q2: How do nutrients from the abiotic to the biotic components of the ecosystem? Q3: How do nutrients flow from the biotic to the abiotic components of the ecosystem? Energy Flow and Nutrient Cycling ● ● Decomposers: return nutrients to the abiotic world by breaking down the bodies of dead organisms Without decomposers: ○ Nutrients could not be repeatedly reused. ○ Life would cease because all essential nutrients would be locked up in dead organisms. Q1: How is a decomposer different from a more typical consumer? Q2: How is energy captured by producers? Q3: Describe all the points at which heat is lost in the figure. What Affects Population Size? ● ● Population: a group of organisms of the same species in a defined area Population size: the total number of individuals in the population ○ Usually changes over time ○ An increase or decrease depends on the number of: ■ Births and deaths in the population ■ Individuals that enter (immigrate) or leave (emigrate) the population ○ Birth and immigration increase population size. ○ Death and emigration decrease population size. Environmental Factors Also Have a Strong Impact on Population Size ● Environmental factors impact population sizes. ○ Lack of space, Food shortages, Predators, Disease, Habitat deterioration ● Carrying capacity: the number of individuals that can live in an environment indefinitely Population Growth Types ● Exponential growth: growth of a population with no constraints on its resources ○ Occurs when a population increases by a constant proportion over a constant time interval (such as one year) ○ Is represented by a J-shaped growth curve ● Logistic growth: growth of a population that approaches its carrying capacity because of constrained resources ○ Occurs with nearly exponential growth at first, but then stabilizes at the maximum population size that can be supported indefinitely by the environment ○ Is represented by an S-shaped growth curve Populations Can Experience Exponential Growth or Logistic Growth ● A population that is not constrained by resources or by the environment can grow exponentially. ● A population that is constrained by a set carrying capacity will show logistic growth. Q1: Which form of population growth displays a J-shaped curve? Q2: Which form of population growth displays an S-shaped curve? Q3: Describe a situation in which a population initially shows exponential growth and later shows logistic growth. Curves of Logistic and Exponential Growth in the World Human Population ● Human population: ○ Began to rise logistically with agriculture in 8000 BCE ○ Growth exploded exponentially in 1800 AD with the industrial revolution ○ Continues to show exponential growth to the detriment of the environment ● The dashed line indicates the United Nations’ estimated carrying capacity of Earth. ○ 9-10 billion people Q1: According to this graph, approximately when did exponential growth begin? Q2: What milestone corresponds to the transition from logistic to exponential population growth? Q3: What is the UN’s projected carrying capacity of Earth, and when will we reach it? Populations of Two Species May Increase and Decrease Together Q1: During which years did the hare likely have the greatest food supply? Q2: Besides the number of hare, what other factors might contribute to the number of lynx? Q3: Can you draw an average carrying-capacity line on these graphs? Why or why not? Species Interdependence ● Ecological communities: associations of species that live in the same area and interact with one another ● A keystone species: a species that has a disproportionately large effect on a community, relative to the species’ abundance. ○ Another example: the sea star Pisaster ochraceus ■ Experiment: Sea stars were removed from one site, while an adjacent site was left undisturbed. Q1: How many species were left in 1966 in the community where sea stars were not removed? Q2: How many species were left in 1966 in the community where sea stars were removed? Q3: How do your answers to questions 1 and 2 demonstrate the importance of a keystone species for the maintenance of diversity in a community? No Wolves = More Elk = Less Aspen Trees ● Wolves eat elk, and elk eat aspen trees. ● ● Food chain: simple list of who eats whom Food web: a more complex diagram of several food chains in a single ecosystem ● ● Producers: organisms at the bottom of a food chain that convert sunlight energy into food energy Consumers: organisms that get energy by eating others below them on a food chain Food Webs Show How Energy Moves Through a Community ● Food webs are composed of many food chains that show one species eating another. Q1: What species eats the coyote? Q2: What species does the coyote eat? Q3: What do you think would happen to a community that lost its coyotes? Producers Are the Energy Base of a Food Chain ● In the wolf-elk-aspen food chain, aspen are the producers: ○ The organisms at the bottom of the food chain that use energy from the sun to make their own food through photosynthesis ○ In Yellowstone, and on land all over Earth, photosynthetic plants are the major producers. ■ Trees, grasses, and shrubs Q1: Where do producers acquire the energy they need to perform their function in the food chain? Q2: Why are producers necessary for life on Earth? Q3: Given the lower abundance of producers in desert regions, compared to tropical rainforests, what would you predict about the abundance of consumers in the two environments? Hierarchy of Consumers ● Consumers: organisms that obtain energy by eating all or parts of other organisms or their remains ○ Primary consumers: Elk eat aspens (producers). ○ Secondary consumers: Wolves eat elk (primary consumers) that ate aspens (producers). ○ Tertiary consumer: A bird that eats a spider (secondary consumer) that ate a beetle (primary consumer) that ate a plant (producer) ○ Quaternary consumer: A killer whale that eats a leopard seal (tertiary consumer) that ate a sea bass (secondary consumer) that ate a krill (primary consumer) that ate a phytoplankton (producer) How do Species Interact? ● There are four central types of species interactions in communities: ○ 1. Mutualism- two species interact: both benefit. ■ Example: clownfish and sea anemone ○ 2. Commensalism- two species interact: one benefits, the other is unharmed. ■ Example: The gray whale’s snout is covered in barnacles ○ 3. Predation- two species interact: one benefits, the other is harmed or destroyed. ■ Predator: consumer that eats part or all of other organisms ● Parasite: a kind of predator that lives in or on the organism it harms, its host ■ Types of predators are distinguished by what they eat: ● Herbivores: animals that eat plants ● Carnivores: animals (and, in rare cases, plants) that kill other animals for food ● Omnivores: eat both animals and plants ○ Scavengers: eat dead or dying plants and animals ■ Decomposers (such as fungi): dissolve their food ■ Detritivores (including worms and millipedes): mechanically break apart and consume their food ■ Example: While the cheetah is what we traditionally think of as a predator, it can also be prey to parasites and, eventually, to decomposers and detritivores. Q1: What kind of predator is the cheetah in the figure? Q2: What kind of predator is the louse in the figure? Q3: What kind of predator are the elk that graze on aspen tree saplings? ○ 4. Competition- two species fight for a common resource. ■ Ecological niche: sert of resources a population needs to survive and reproduce ■ Competition: occurs when two species share (fight for) a limited resource and the success of one species excludes another ■ The competitive exclusion principle predicts that different species that use the same resource can coexist only if one of the species adapts to using other resources. ● Example: ○ Elk and bears also interact through exploitative competition where they compete for berry-producing shrubs. ○ Elk eat the leaves and branches on shrubs, resulting in a decrease in the number of berries for the grizzlies to eat. ○ The percentage of berries in the grizzly diet went up as elk populations went down. ○ Grizzlies adapted to the presence of elk by finding food sources other than berries, and in the absence of elk they increased their consumption of berries. Q1: Which species appears to be the superior competitor in the map shown?