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Ch 35 Population/ Community Ecology 35.1 Population Density Population density is the number of individuals of a particular species per unit area or volume. Examples: 35 alligators per square km of a swamp 1,000,456 bacteria per cm2 of an agar plate 120 earthworms m2 of soil Population density problems On rare occasions you can count all the individuals in a population, such as the number of beech trees in a forest measuring 50 square kilometers (km2). Population density = Individuals = 1000 trees = 20 trees Unit area 50 km2 km2 Population density is a helpful measurement for comparing populations in different locations. Population Dispersion 35.2 There are limits to a population’s growth Exponential growth: growth of a population that multiplies by constant factor Limiting factor:condition that restricts a population’s growth, such as space, disease and food availability. Carrying capacity: number of organisms in a population that an environment can maintain. Exponential Growth Figure 35-5 This table shows how many bacteria are in a population that doubles every 20 minutes. The graph is another way to show the same data. CARRYING CAPACITY Figure 35-6 Figure 35-6 Before the early 1900s, hunting kept this population of fur seals below the carrying capacity of the environment. Then, after hunting was reduced, the population grew almost exponentially for two decades. The population began to level off as it reached the carrying capacity. Changes in Population Size Growth factors (increase in pop.) Immigration: individuals moving into a population Births Shrinking factors (decrease in pop.) Emigration: individuals moving out of a population Deaths Exponential Growth= J curve Early phase of growth High availability of resources Little competition Little predation Logistic Growth= S curve represent Carrying capacity Limits on growth appear Competition for resources Predation Parasitism Illness 35.3 Human Population Growth The human population is now growing at a rate of about: 3 people/second or 260 thousand/day or 1.8 million per week or 93 million/year Earth’s Carrying Capacity about 50 Billion Human Population Growth Are humans in exponential or logistic growth? 35.4 Interactions in Communities Competition Between Species An elephant, cannot survive without other organisms. elephant herd of elephants (population) an elephant’s community An elephant’s community = gazelles, giraffes, birds, ants, beetles, fungi, bacteria, grasses, trees Members of a population compete for limited resources in the environment. -Competition within a single species limits the growth of the population. Interspecific competition: when two or more species rely on the same limited resource (competition between 2 different species) example:during times of drought in an African savanna community, grasses may be in short supply, and competition becomes intense. Competitive Exclusion Competitive exclusion: One species succeeding over another, when the growth of both species is limited by the same resource. Figure 35-14 Two similar species may each thrive in separate locations, but one may exclude the other when they are placed together. The results of an experiment with two Paramecium species demonstrate this principle of competitive exclusion. NICHE Niche: a unique living arrangement of an organism defined by its living place (habitat), its food sources, the time of day it is most active, and other factors The local loss of a species is likely to occur if 2 species have niches that are very similar niches are rarely identical. Example: one lizard in a tropical forest feeds on insects in low shrubs, while a similar lizard may eat insects high in the trees. Predation Predation: an interaction in which one organism eats another. The lion attacks and eats an injured zebra or an egret catches and eats a fish. Predator: the organism that kills/ eats the prey. Prey: the organism that gets eaten. eating and avoiding being eaten are important to survival, many effective adaptations have evolved in both predators and prey. Predator/ Prey Predator Adaptations fast and agile camouflage teaming up in packs acute senses claws, teeth, fangs, and stingers Ex. Rattlesnakes locate their prey with heat-sensing organs located between each eye and nostril. Prey Adaptations retreat to safe locations flee from predators camouflage to hide "warning coloration" is a caution to predators. mimicry -look like organisms that are poisonus or dangerous. Plants have poisonous chemicals and structures such as spines and thorns. Warning Coloration Monarch w/ warning coloration Viceroy Butterfly- mimics Monarch Symbiotic Relationships Symbiotic relationship is a close interaction between species in which one of the species lives in or on the other. 3 main types of symbiotic relationships: parasitism, mutualism, and commensalism. 1.) Parasitism is a relationship in which the parasite obtains its food at the expense of the host. Usually the parasite is smaller than the host. (blood- sucking mosquitoes and tapeworms) Ticks Mutualism: both organisms benefit from the symbiotic relationship. Your large intestine is inhabited by millions of bacteria. The bacteria benefit by having a warm, moist home and food. Intestinal bacteria produce vitamin K. Vitamin K is essential for blood clotting. Both you and the bacteria benefit from this relationship. Mutualism Manta with Remoras Pair ofRay Coleman Shrimp on fire urchin Commensalism is a relationship in which one organism benefits, while the other organism is neither harmed nor helped significantly. Example: A spider crab may place seaweed on its back. The crab benefits by being camouflaged from its predators. The seaweed is not affected. commensalism in nature is rare, since most interactions harm one species (parasitism) or help both species (mutualism) to some degree. Commensalism 35.5 Disturbances are common in communities Ecological Succession Ecological succession. Series of changes in the species of a community, often followed by a disturbance. Primary Succession- process by which a community arises in a lifeless area that has no soil barren ground lichen/mosses grass shrubs pine trees hardwood trees Examples: Forest devastated by a fire, or volcano new islands created by erupting volcanoes bare rock left behind a retreating glacier. Primary Succession The establishment and development of an ecosystem in an area that was previously uninhabited Lichens and mosses Grasses And small shrubs Large shrubs and small trees Large trees Primary Succession Surtsey: A Case Study The island of Surtsey formed by volcanic eruption off of the coast of Iceland during the period from 1963 - 1967 Surtsey – Post Eruption Surtsey Today Secondary Succession Secondary succession when a disturbance damages an existing community but leaves the soil intact Grasses shrubs trees similar to the original forest. Example: when a forested area is cleared for farming and then abandoned. Secondary Succession The recovery of a damaged ecosystem in an area where the soil was left intact Fireweed Sequoia seedling Case Study: Yellowstone National Park 1988 – Devastating forest fires burn much of Yellowstone National Park. Photo: National Parks Service Yellowstone National Park 1988 – Park map showing areas (1.6 million acres) burned by the series of fires. Yellowstone National Park 1988 fires – The immediate aftermath. Photo: National Parks Service Yellowstone National Park One year after the fires Note the appearance of fireweed Photo: National Parks Service Yellowstone National Park Ten years after the fires (1998) Photo: National Parks Service Yellowstone National Park Twenty years after the fires (2008) Case Study - Chernobyl In April, 1986, a nuclear power plant in the former USSR experienced a core meltdown and a catastrophic release of radioactivity into the environment. Chernobyl Surrounding towns and villages had to be immediately, permanently abandoned. Chernobyl – Twenty Years Later Chernobyl – Twenty Years Later Pripyat town square. Chernobyl – Twenty Years Later Pripyat Soccer Stadium opened in 1986. Chernobyl – Twenty Years Later A local highway. Secondary succession: trees are colonizing uncultivated fields and meadows Human Activities and Species Diversity humans have had the greatest impact on communities worldwide. 60 % Earth's land is used by humans, mostly as cropland or rangeland. Human disturbances have a negative effect on species diversity Clearing the Land for lumber land for farming Land for building. paved over or eventually recolonized by weeds and shrubs, as in abandoned city lots. Invasive Species Courtesy www.lab-initio.com Invasive Species Introduced species: any organism that was brought to an ecosystem as the result of human actions Invasive species: A species that takes advantage of an unoccupied niche, or that successfully out-competes native species Kudzu: an invasive vine Introduced Species Introduced species are organisms that humans move from the species' native locations to new geographic areas, either intentionally or accidentally (exotic species). Kudzu, a Japanese plant planted widely in the American South (1930s) to help control erosion. especially along irrigation canals. But kudzu soon grew out of control, taking over vast expanses of landscape. Some introduced species gain a foothold and may disrupt their new community. Some introduced species prey on native species or outcompete native species Invasive species Invasive species are "alien” species whose introduction does or is likely to cause economic or environmental harm or harm to human health" U.S. Invasive Aquatic Plants Partial list: Brazilian Waterweed Caulerpa, Mediterranean Clone Common Reed Eurasian Watermilfoil Didymo Giant Reed Giant Salvinia Hydrilla Melaleuca Purple Loosestrife Water Chestnut Water Hyacinth Water Lettuce Water Spinach Hydrilla U.S. Invasive Aquatic Animals Partial list: Alewife New Zealand Mud Snail Northern Snakehead Asian Carps Nutria Asian Swamp Eel Quagga Mussel Bullfrog Round Goby Chinese Mitten Crab Rusty Crayfish Eurasian Ruffe Sea Lamprey European Green Crab Sea Squirt Flathead Catfish Spiny Water Flea Lionfish Veined Rapa Whelk Zebra Mussel Zebra Mussel U.S. Invasive Invertebrates Partial list: Africanized Honeybee Asian Citrus Psyllid Asian Long-Horned Beetle Asian Tiger Mosquito Cactus Moth Emerald Ash Borer European Gypsy Moth European Spruce Bark Beetle Formosan Subterranean Termite Giant African Snail Glassy-Winged Sharpshooter Hemlock Woolly Adelgid Light Brown Apple Moth Mediterranean Fruit Fly Mexican Fruit Fly Pink Hibiscus Mealybug Red Imported Fire Ant Russian Wheat Aphid Silverleaf Whitefly Sirex Woodwasp U.S. Invasive Vertebrates Partial list: Widespread At Risk of Brown Tree Snake Intrusion Cane Toad snakes European Starling snakes Wild Boar rat House Sparrow Nutria Constrictor Boiga Gambian pouch European Starling Cane Toad U.S. Invasive Plants Autumn Olive Beach Vitex Canada Thistle Chinese Tallow Cogongrass Common Teasel Dalmatian Toadflax Diffuse Knapweed Downy Brome Garlic Mustard Giant Hogweed Hairy Whitetop Houndstongue Japanese Honeysuckle Japanese Knotweed Johnsongrass Kudzu Leafy Spurge Medusahead Mile-A-Minute Weed Multiflora Rose Musk Thistle Old World Climbing Fern Oriental Bittersweet Purple Star Thistle Quackgrass Russian Knapweed Russian Olive Saltcedar St. Johnswort Scotch Broom Scotch Thistle Spotted Knapweed Tree-of-Heaven Tropical Soda Apple Whitetop Yellow Star Thistle Yellow Toadflax Yellow Star Thistle U.S. Invasive Microbes Animal Pathogens Avian Influenza Exotic Newcastle Disease Fowlpox Viral Hemorrhagic Septicemia West Nile Virus Whirling Disease Plant Pathogens Citrus Canker Citrus Greening Plum Pox Southern Bacterial Wilt Soybean Rust Sudden Oak Death West Nile Virus Citrus Canker Kudzu vines Zebra Mussels clogging pipes Zebra mussels clogging pipe 35.5 DISTURBANCES Definitions Bioaccumulation: is the process by which substances not readily broken down or excreted can build up and be stored in living tissue (usually in fatty tissue.) Biomagnification: is the process by which substances become more concentrated in the bodies of consumers as one moves up the food chain (trophic levels). Case Study: PCBs PCBs, or polychlorinated biphenyls, are a group of manmade chemicals. Introduced in 1929 and widely used in electrical transformers, cosmetics, varnishes, inks, carbonless copy paper, pesticides and for general weatherproofing and fire-resistant coatings to wood and plastic. The federal government banned the production of PCBs in 1976 PCBs can effect the immune system, fertility, child development and possibly increase the risk of certain cancers DDT is a pesticide that was widely used until being banned in the U.S. in 1972 DDT accumulates in living tissue, particularly in fat tissue High concentrations in some bird species caused failure of eggs by thinning the shells Case Study: DDT Case Study: Methyl Mercury What makes methylmercury so dangerous? Methylmercury is rapidly taken up but only slowly eliminated from the body by fish and other aquatic organisms, so each step up in the food chain (bio)magnifies the concentration from the step below. Bioaccumulation factors (BAF's) of up to 10 million in largemouth bass have been reported for the Everglades. Fish-eating birds, otters, alligators, raccoons and panthers can have even higher bioaccumulation factors. U.S. Department of the Interior, U.S. Geological Survey, Center for Coastal Geology This page is: http://sofia.usgs.gov/sfrsf/rooms/mercury/achilles_heel/cause.html Mercury Health Effects
