Standard 3 Interdependence of Living Systems & the EnvironmentUnit 8 Population Ecology & Human Impacts on Ecosystems Objectives B3.4A: Describe ecosystem stability. Understand that if a disaster such as flood or fire occurs, the damaged ecosystem is likely to recover in stages of succession that eventually result in a system similar to the original one. B3.4C: Examine the negative impact of human activities. B3.5B: Explain the influences that affect population growth Questions How much longer will petroleum resources last?
What effect is the population having on the water system? What is the effect of recycling paper and aluminum cans? Central & South America
Estimated world population at various dates, in thousands Human Population Year World Africa Asia Europe Central & South America Northern America* Oceania notes 8000 BC 5 000 [5] 1000 BC 50 000 500 BC 1 AD 200,000 plus [6] 1000 310000 1750 791000 106000 502000 163000 16000 2000 1800 978000 107000 635000 203000 24000 7000 1850 1262000 111000 809000 276000 38000 26000 1900 1650000 133000 947000 408000 74000 82000 6000 1950 2518629 221214 1398488 547403 167097 171616 12812 1955 2755823 246746 1541947 575184 190797 186884 14265 1960 3021475 277398 1701336 604401 218300 204152 15888 1965 3334874 313744 1899424 634026 250452 219570 17657 1970 3692492 357283 2143118 655855 284856 231937 19443 1975 4068109 408160 2397512 675542 321906 243425 21564 1980 4434682 469618 2632335 692431 361401 256068 22828 1985 4830979 541814 2887552 706009 401469 269456 24678 1990 5263593 622443 3167807 721582 441525 283549 26687 1995 5674380 707462 3430052 727405 481099 299438 28924 2000 6070581 795671 3679737 727986 520229 315915 31043 2005 6453628 887964 3917508 724722 In Closed Populations, Growth Rate is Determined by the Difference Between Birth and Death Rates
r = birth rate death rate Population Growth Reflects the Balance Between Birth and Death Rates
For example, Mexicos population has grown explosively even though its birth rate has declined Immigration and Emigration Can Strongly Effect Population Dynamics
Estimated rates of US population growth with or without immigration. A Populations Age Structure Determines Its Potential for Growth
Populations with a pyramid-shaped age structure will grow explosively. Populations with a rectangular age structure will grow much slower. Generally, human populations in the developed world are rectangular and those of developing nations are pyramidal. The Worlds Human Population Has Grown Explosively in the Past 200 Years
Continued rapid human population growth is one of the greatest strains on the health of ecosystems and humanity. Human Population Growth Is Unevenly Distributed
The recent increase in human population in the developing world is due primarily to decreased death rate, not increased birth rate. Human Population Density Varies Widely The Carrying Capacity for Human Populations Is Unknown
Although a precise figure isnt known, its clear that carrying capacity is influenced by technology. World Population Growth is Slowing
The major factor is declining fertility rates. World Population Growth is Slowing
Population structure of Kenya in 2000 and projections for 2050. BIOMAGNIFICATION Biomagnification = a substance gets more concentrated as it passes through the food chain.Example DDT The concentration effect occurs because DDT is metabolized and excreted much more slowly than the nutrients that are passed from one trophic level to the next. So DDT accumulates in the bodies (especially in fat). Thus most of the DDT ingested as part of gross production is still present in the net production that remains at that trophic level. Biomagnification is the bioaccumulation of a substance up the food chain by transfer of residues of the substance in smaller organisms that are food for larger organisms in the chain. It generally refers to the sequence of processes that results in higher concentrations in organisms at higher levels in the food chain (at higher trophic levels). These processes result in an organism having higher concentrations of a substance than is present in the organisms food. Biomagnification (00:59) Succession Succession = gradual change of a site into a different ecosystem Pond Swamp Meadow Forest Stages of Succession (01:14) Primary Succession at Glacier Bay, Alaska
Factors That Influence Succession (05:46) A climax community is the stable community at the final stage of succession. Sand Dune Succession Where a series of dunes has formed at the back of a beach, the youngest dunes will be closest to the shore and the oldest furthest away. This is one of the few examples where all the stages of a succession can often be clearly seen in one place. Pioneer Stage Foredunes Yellow (White) Dune Stage Conifer Plantations Dune Building Model of Dry Dune Succession
Dunes' stages can be connected, but they don't have to be. A single dune can go through all the stages without having another dune next to it. However, most of the dunes are connected to other dunes often in other stages of Succession. New dunes are constantly being formed near the beach, as seen above, a dune has just started Succession, although it has been growing for many years. Natures Complexity Hierarchical Organization Landscapes Ecosystems
Communities Species Populations Individuals Organ systems Organs Organ tissues Cells Cell organelles Molecules LESS understanding = Ecologists realm MORE understanding Population Ecology Scientific study of individual populations and their interaction with, or response to, the environment. Population = all the individuals within a species Carrying Capacity = the population or # of individuals an ecosystem can hold/sustain Sustainability = the ability of an ecosystem to support a population indefinitely Population size Time Learning Ecological Terms (07:23) Populations Communities - Ecosystems
Organisms of one species form a population. Populations of different organisms interact to form communities. Living communities and the nonliving factors that interact with them form ecosystems. List all components (biotic & abiotic) in a pond ecosystem Population and Community (02:19) Levels of Ecological Investigation Population Ecology A population is a group of individuals of the same species that occupy a specified region at a specified time. Key questions of population ecology include: What is the size of a population? What is the potential for growth in the population? What form will growth take? Community Ecology Community ecology examines the question of how populations interact. Questions include: What are the types of species and their numbers within a community (i.e. community structure)? Are there especially critical species for maintenance of the community? What is the relationship (predator, prey, parasite) between species within the community? Community Ecology The study of groups of species that live together in a particular area or habitat. Habitat = place where a species lives (human habitat = house) Habitats (00:38) Populations, Habitats, and Niches (03:30) Interspecific Interactions + / oCommensalism + / +Mutualism + / -Parasitism Parasitoidism Herbivory + / - -Predation - / -Competition Types of Interactions Within Ecosystems (04:35) Interdependency Two organisms can be mutually beneficial and that can lead to interdependency. Interdependency = mutuality: a reciprocal relation between interdependent entities (objects or individuals or groups). Apples & Honey Bees Mutualism Mutualism occurs when species interact in a mutually beneficial manner. The oxpecker gets food (ticks and insects disturbed in the grass) and a safe haven from the rhinoceros, and the rhinoceros has parasites (ticks) removed. Relationships Between Populations: Symbiotic (02:30) Mutualism Mycorrhizal fungi (threads) covering aspen roots: fungi aid in water and nutrient absorption by the aspen and the aspen provides sugars and other food molecules to the fungi. Parasites A parasite is an organism that lives in or on the living tissue of a host organism at the expense of that host. The biological interaction between the host and the parasite is called parasitism. A parasite is an animal or plant that lives in or on a host (another animal or plant); it obtains nourishment from the host without benefiting or killing the host Tapeworm Whipworm Parasites Almost everyone has parasites. Its simply a fact of life. Even Dr. Oz, the now famous Oprah Winfrey guest says..."ninety percent of humans will have a problem with parasites in their lifetime." Parasites are not just something that other people get a malady reserved for citizens of developing countries. Everywhere we go, during just about everything we do, North Americans are vulnerable to parasitic infestation. The World Health Organization (WHO) classifies parasites as among the six most dangerous diseases that infect humans. Parasites outrank cancer as the number one global killer, and account for many of the digestive woes from which people suffer. Hookworm Roundworm Mosquito Parasitic Worms of the Animal Kingdom (05:06) Parasites Homework - Diagram the stages of the life cycle for a human disease-causing organism. Biodiversity There are many measures of biodiversity.
Considering species diversity, more diverse communities tend to be more productive. The role of diversity in community stability is less clear. Biodiversity Remember, however, that this is one set of communities. Why Worry About the Relationship Between Biodiversity and Community Stability?
Because this understanding is essential for knowing how many species and of what types can be lost before a community collapses. Connected Systems: Biodiversity, Ecosystems, and Ecology Biodiversity Varies Naturally
There is a trend towards more species in warmer, wetter areas and fewer in colder and drier areas. Why Should We Care? (04:22) Numbers of bird species occupying areas of North America. We really dont have a satisfying answer to this fundamental question.
Science (2005) 309:90 We really dont have a satisfying answer to this fundamental question. There are Biodiversity Hotspots
Biodiversity hotspots for tropical rain forest and chaparral ecosystems. Less than 1% of Earths surface supports 20% of known plant species and probably a greater portion of animal species. Biodiversity hotspots are significant for conservation plans. Biodiversity is Being Lost Rapidly Through Extinction
How rapid is the current rate of extinction? The numbers hard to pin down, but generally accepted estimates put it at times the rate before extensive humaninduced environmental modifications. For example, in the U.S. ~ 225 vascular plant species have become extinct in the past 50 years and about 650 of the remaining 20,000 species are threatened. Community Ecology Predator-Prey Relationship = 2 species have a relationship where the population of one affects the population of the other one The predators -- eat the other -- the prey Such pairs exist throughout nature: lions and gazelles, birds and insects, pandas and bamboo, Venus fly traps and flies Predator-Prey Relationships: The Example of the Bobcat and Rabbit (01:44) Predator-Prey Equilibrium As the number of carnivores in a community increases, they eat more and more of the herbivores, decreasing the herbivore population. It then becomes harder and harder for the carnivores to find herbivores to eat, and the population of carnivores decreases. In this way, the carnivores and herbivores stay in a relatively stable equilibrium, each limiting the other's population. A similar equilibrium exists between plants and plant-eaters. Predation, Parasitism and Coevolution
Predation (consuming another organism) and parasitism (feeding upon a host organism without causing its immediate death) drive an evolutionary arms race. Predator and prey, host and parasite are locked in a duel to outwit their opponent through adaptations. Predator and prey interactions drive coevolution coupled adaptive changes in interacting species. Reproductive Strategies
Describe different reproductive strategies employed by various organisms and explain their advantages and disadvantages. Although every organism struggles to survive, individual survival is not enough to ensure continuation of the species. Individuals must reproduce. Scientists have identified two strategies for leaving living descendants. These strategies are called the r-strategy and the k-strategy. Some organisms, animals and plants, use one strategy or the other: some seem to tend towards one but are closer to a sort of mid-point. Let's compare these strategies. Hint - Remember that R stands for Rapid so that you will remember which strategy is which. R-Selected parents rapidly produce many descendents, but do not provide care for them. Reproductive Strategies
r-selected K-selected mature rapidly mature slowly short-lived:most die before they reproduce tend to live long lives: low juvenile mortality rate compete well for resources have many offspring - tend to overproduce have few offspring at a time invest little in individual youngsters care for their young most pest species are r-selected most endangered species are K-selected population not regulated by density:boom and bust population figures population stabilizes near carrying capacity opportunistic -- invade new areas maintain numbers in stable ecosystems Reproductive Strategies
We see that r-selected organisms have many babies, but most of these youngsters never become adults. Frogs are a good example of r-selected organisms. Frogs lay many eggs and leave them in the water to hatch into tadpoles. Some of the eggs get eaten, and many of the little tadpoles are eaten, too, by dragon-fly larvae and fishes and fishing birds. When the tadpoles become frogs, many animals are waiting on shore to eat them: raccoons, foxes, snakes, cats, and many other small predators. If one frog from a hundred eggs lives to be a parent, his/her survival is really outstanding. But frogs go on because they lay so many eggs. Reproductive Strategies
Elephants are examples of K-selected animals. Female elephants have babies about three years apart, and they have only one each time. The whole group looks after the youngsters, and protects them through childhood and adolescence. By reproducing at a rate that holds their numbers close to constant, elephants are able to survive in stable ecosystems. Because they ensure the survival of a good percentage of their young, elephants do not need to produce many elephant babies Reproductive Strategies - Farm
Cattle - Heifers become sexually mature cows at between 15 and 27 months; bulls are mature at 1 year. Gestation is about 9 months. Cows can't be milked unless they have given birth, so each female is expected to produce at least 1 living calf every year. In the U.S. beef cattle calves are usually born in the spring; they stay with their mothers until weaned and are sold off in the fall.Cows have a calf in the spring and are breed again in early summer when the calf is only about 3-4 months old. Swine - Sexual maturity of a gilt can be reached between 8 and 10 months of age.Sows usually have litters of from 1 to 15 young, generally 8 being average. Females are extremely protective of their young.Gestation is 3 months, 3 weeks, 3 days.Piglets are weaned after an average of 4-5 weeks.The sows will recondition and get rebreed to have their second litter for the year. Mouse - Sexually mature at 4-7 weeks (both males and females) with a life expectancy of 1-3 years. Cycle of heats every 4-5 days, continuing all year round with a gestation period of19-21 days.Average size of litter is 4-14 (even more), averaging 12 babies which they nurse for approximately weeks.They are weaned at males 3,5 weeks, females may be weaned at 4 weeks. They then separate to single sex groups at 3.5 weeks and are ready to leave for new homes at 1 month of age.Females experience a resting period between matings of at least 2 weeks, preferably over 1 month between weaning of one litter and mating for another. Invasive Species Predict the consequences of an invading organism to the survival of other organisms. The term invasive species refers to a subset of introduce species or non-indigenous species that are rapidly expanding outside of their native range. Invasive species can alter ecological relationships among native species and can affect ecosystem function and human health. A species is regarded as invasive if it: (1) has been introduced by human action to a location where it did not previously occur naturally, (2) becomes capable of establishing a breeding population in the new location without further intervention by humans, and (3) spreads widely throughout the new location. In simple terms, an invader has to (1) arrive, (2) survive, and (3) thrive. Invasive Species in Michigan
Crustaceans: Cercopagis pengoi | Rusty Crayfish | Spiny Water Flea Fish: Common Carp | Goby | Ruffe | Sea Lamprey | White Perch Mollusks: Zebra Mussel Plants: Curly-leaf Pondweed | Eurasian Watermilfoil | Flowering Rush | Purple Loosestrife Insects: Emerald Ash Borer / Japanese Beetle / Asian Longhorn Beetle Fungus:Soybean Rust Invasive Species The emerald ash borer is an Asian beetle that entered the U.S. in the mid-1990s near Detroit, though it was not officially identified until It probably arrived in wood packing commonly used to ship all manner of goods. Adult female EABs lay eggs in the crevices of the bark of ash trees. After the eggs hatch, the larvae bore into the tree and eat the cambium layer between the bark and wood. Over time, the galleries created by the borers' feeding activities girdle and eventually kill branches and entire trees. An infested tree typically dies within two to three years. Green ash, white ash, black ash and several horticultural varieties are susceptible to damage by the emerald ash borer. Invasive Species Zebra mussels (Dreissena polymorpha) are small, fingernail-sized mussels native to the Caspian Sea region of Asia. They are believed to have been transported to the Great Lakes via ballast water from a transoceanic vessel. The ballast water, taken on in a freshwater European port was subsequently discharged into Lake St. Clair, near Detroit, where the mussel was discovered in Since that time, they have spread rapidly to all of the Great Lakes and waterways in many states, as well as Ontario and Quebec.Diving ducks and freshwater drum eat zebra mussels, but will not significantly control them. Likely means of spread: Microscopic larvae may be carried in livewells or bilgewater. Adults can attach to boats or boating equipment that is in the water. Zebra Mussels and Other Invasive Species in the Great Lakes Basin (01:56) Invasive Species Purple Loosestrife (Lythrum salicaria) is a wetland plant from Europe and Asia. It was introduced into the east coast of North America in the 1800s. First spreading along roads, canals and drainage ditches, then later distributed as an ornamental, this exotic plant is in 40 states and all Canadian border provinces. The plant can form dense, impenetrable stands that are unsuitable as cover, food or nesting sites for a wide range of native wetland animals, including ducks, geese, rails, bitterns, muskrats, frogs, toads and turtles. Many rare and endangered wetland plants and animals also are at risk. Likely means of spread: Seeds escape from gardens and nurseries into wetlands, lakes and rivers. Once in aquatic systems, seeds are easily spread by moving water and wetland animals. Ecosystem Ecology Simple ecosystem model ECOSYSTEM = The living (biotic) and nonliving (abiotic) organisms which affect the existence of other animals and plants Introduction to Ecosystems and Their Environment (01:44) Dynamics Within the Ecosystem
The physical or chemical environment may influence the rate, extent, and nature of population dynamics within ecosystems. Human welfare ultimately depends in many ways on ecosystem functioning. Most ecosystems on earth are under the influence of physical and chemical stressors, and face a steady change of concentrations and effects of a whole suite of polluting substances. Ecosystem components Plants Decomposers Animals Abiotic components:
Water Atmosphere Soil minerals Why should we care about ecosystem ecology?
Ecosystem ecology provides a mechanistic basis for understanding the Earth System Ecosystems provide goods and services to society Human activities are changing ecosystems (and therefore the Earth System) Human Impact Humans have a tremendous impact on the environment.Sometimes their impact is beneficial, and sometimes it is detrimental. Greenhouse Effect What is the greenhouse effect? The greenhouse effect is a natural warming process of the earth. When the sun's energy reaches the earth some of it is reflected back to space and the rest is absorbed. The absorbed energy warms the earth's surface which then emits heat energy back toward space as longwave radiation. This outgoing longwave radiation is partially trapped by greenhouse gases such as carbon dioxide, methane and water vapour which then radiate the energy in all directions, warming the earth's surface and atmosphere. This is the greenhouse effect. Increasing the amount of greenhouse gases intensifies the greenhouse effect. Higher concentrations of CO2 and other greenhouse gases trap more infrared energy in the atmosphere than occurs naturally. The additional heat further warms the atmosphere and Earths surface. Climate models suggest this natural warming is being enhanced by human activities that increase concentrations of greenhouse gases in the atmosphere and greenhouse effect. The increase in atmospheric concentration of greenhouse gases, accentuating the natural greenhouse effect globally, is also called the enhanced greenhouse effect or Global Warming. Were in the Drivers Seat - Human Activities Dominate Many Biogeochemical Cycles Global Warming Here's the lowdown on why it's happening, what's causing it, & how it might change the planet. Is It Happening? Yes. Earth is already showing many signs of worldwide climate change. Average temperatures have climbed 1.4 degrees Fahrenheit (0.8 degree Celsius) around the world since 1880, much of this in recent decades, according to NASA's Goddard Institute for Space Studies. The rate of warming is increasing. The 20th century's last two decades were the hottest in 400 years and possibly the warmest for several millennia, according to a number of climate studies. And the United Nations' Intergovernmental Panel on Climate Change (IPCC) reports that 11 of the past 12 years are among the dozen warmest since 1850. The Arctic is feeling the effects the most. Average temperatures in Alaska, western Canada, and eastern Russia have risen at twice the global average, according to the multinational Arctic Climate Impact Assessment report compiled between 2000 and 2004. Global Warming Is it happening?
Arctic ice is rapidly disappearing, and the region may have its first completely ice-free summer by 2040 or earlier. Polar bears and indigenous cultures are already suffering from the sea-ice loss. Glaciers and mountain snows are rapidly meltingfor example, Montana's Glacier National Park now has only 27 glaciers, versus 150 in In the Northern Hemisphere, thaws also come a week earlier in spring and freezes begin a week later. Coral reefs, which are highly sensitive to small changes in water temperature, suffered the worst bleachingor die-off in response to stressever recorded in 1998, with some areas seeing bleach rates of 70 percent. Experts expect these sorts of events to increase in frequency and intensity in the next 50 years as sea temperatures rise. An upsurge in the amount of extreme weather events, such as wildfires, heat waves, and strong tropical storms, is also attributed in part to climate change by some experts. Global Warming Are humans causing it?
"Very likely," the IPCC said in a February 2007 report. The report, based on the work of some 2,500 scientists in more than 130 countries, concluded that humans have caused all or most of the current planetary warming. Human-caused global warming is often called anthropogenic climate change. Industrialization, deforestation, and pollution have greatly increased atmospheric concentrations of water vapor, carbon dioxide, methane, and nitrous oxide, all greenhouse gases that help trap heat near Earth's surface. Humans are pouring carbon dioxide into the atmosphere much faster than plants and oceans can absorb it. These gases persist in the atmosphere for years, meaning that even if such emissions were eliminated today, it would not immediately stop global warming. Some experts have said that a natural cycle of planetary warming and cooling that alters the amount of sunlight falling on Earth may explain the trend. The planet has indeed experienced such cycles roughly every hundred thousand years, but such changes in the past have manifested themselves over the span of several centuries. Today's changes have taken place over the past hundred years. Other recent research has ruled out variations in solar output as a probable cause. Global Warming What's Going to Happen?
A follow-up report by the IPCC released in April 2007 warned that global warming could lead to large-scale food and water shortages and have catastrophic effects on wildlife. Sea level could rise between 7 and 23 inches (18 to 59 centimeters) by century's end, the IPCC's February 2007 report projects. Rises of just 4 inches (10 centimeters) could flood many South Seas islands and swamp large parts of Southeast Asia. Some hundred million people live within 3 feet (1 meter) of mean sea level, and much of the world's population is concentrated in vulnerable coastal cities. In the U.S., Louisiana and Florida are especially at risk. Glaciers around the world could melt, causing sea levels to rise while creating water shortages in regions dependent on runoff for fresh water. Early light strikes mountains in Montana's Glacier National Park. When the park was created in 1910, it had 150 glaciers. Today, due to melting caused by warming temperatures, there are 30 much smaller glaciers in the park. Global Warming What's Going to Happen?
Strong hurricanes, droughts, heat waves, wildfires, and other natural disasters may become commonplace in many parts of the world. The growth of deserts may also cause food shortages in many places. More than a million species face extinction from disappearing habitat, changing ecosystems, and acidifying oceans. The ocean's circulation system, known as the ocean conveyor belt, could be permanently altered, causing a mini-ice age in Western Europe and other rapid changes. At some point in the future, warming could become uncontrollable by creating a so-called positive feedback effect. Rising temperatures could release additional greenhouse gases by unlocking methane in permafrost and undersea deposits, freeing carbon trapped in sea ice, and causing increased evaporation of water. Greenhouse Gases and Global Warming A Warming World How are humans part of an ecosystem?
What factors contribute to human population growth? What are the implications of having a large human population? How do humans interact with the environment? How are humans and the environment dependant on each other? What is sustainable development? How are humans part of the biotic community?
What factors limit the biotic life of a community? What is the biosphere? What is homeostasis & the impact it has on the environment? What are some consequences of human alterations to the environment? What Are the Concerns? Global warming. Loss of biodiversity.
Change in species distribution. Collapse of ecosystems. Degradation and collapse of human societies. An Uncertain Future? Of course
. but thats not to say theres no hope.