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Section 4.1 Population Dynamics pg.91-99 Chase Upshaw Principles of Population Growth A population is a group of organisms, all of the same species, that live in a specific area Scientists study changes in populations in a variety of ways Ex. Introducing organisms into a controlled environment with abundant resources; observe how the organisms react How fast do populations grow? Starts out slowly then increases rapidly; resembles a J shape on a chart of population growth Starts out small because the number of individuals reproducing is small Then, the numbers become larger over time after constant reproduction Is growth unlimited? Exponential growth- means that as a population gets larger, it also grows at a faster rate Results in unchecked growth What can limit growth? Population growth does have limits Limiting factors such as availability of food, disease, predators, or lack of space, will cause growth to slow Creates a S-shaped growth curve Carrying capacity Carrying capacity- the number of organisms of one species that an environment can support indefinitely When a population is developing in an environment with resources, there are more births than deaths and the population increases until the carrying capacity is reached or passed When carrying capacity is overshot, limiting factors come into place Fluctuating line on a graph of population growth Reproduction Patterns Life-history pattern- an organism’s reproductive pattern Slow life-history pattern- slow rate of reproduction; few offspring Rapid life-history pattern- rapid reproduction; many offspring in a short period of time Rapid life-history patterns Common in organisms from changeable or unpredictable environments Characteristics of rapid life-history pattern organisms Small body size Mature rapidly Reproduce early Short life span Populations increase rapidly and are easily affected by environmental changes Slow life-history patterns Characteristics of slow life-history pattern organisms Larger species Live in more stable environments Reproduce and mature slowly Long life expectancy Density factors and population growth Dispersal of organisms: random, clumped, and uniform can determine limiting factors Density-dependent factor- limiting factors such as disease, parasites, or food availability that affect growth of a population Density-independent factor- factor such as temperature, storms, floods, drought, or habitat disruption that affects all populations, regardless of their density Organism Interactions Limit Population Size Population sizes are not only limited by abiotic factors, but by biotic factors too Predation affects population size When a predator consumes prey on a large enough scale, it can have a drastic effect on the size of the prey population Populations of predators and their prey are known to experience cycles or changes in their numbers over periods of time Ex. Hare and Lynx In prey populations, usually the young, old, and injured organisms are caught Competition within a population Competition is a density-dependent factor When only few individuals compete for resources no problem arises When the demand of resources exceeds supply, then competition increases and population size decreases The effects of crowding and stress When an environment becomes crowded, organisms may exhibit symptoms of stress Symptoms include: Aggression Decrease in parental care Decreased fertility Decreased resistance to disease Section 4.2 Human Population pg.100-103 Chase Upshaw World Population Census is taken every ten years in the United States Provides a picture of how many people there are in the United States, their economic condition, and where they live The United Nations Population Division tracks similar information on all the countries of the world Demography- the study of human population size, the density and distribution, movement, and its birth and death rates Human population growth Human population growth is the result of humans consciously changing their environment As a result, humans live longer and are able to produce offspring that live long enough to produce offspring, hence, a population grows Calculating growth rate Birthrate- the number of live births per 1000 population in a given year Death rate- the number of deaths per 1000 population in a given year (Birthrate + Immigration rate) – (Death rate + Emigration rate) = Population Growth Rate Birthrate – Death rate = Population Growth Rate Doubling time Doubling time- the time needed for a population to double in size Depends on the current size of the population and the growth rate Age structure Age structure- refers to the proportions of the population that are in different age levels Age structure info is used to determine how fast a population will increase or grow Ecology and growth Some countries are concerned with providing the most basic needs Other countries worry about maintaining healthy conditions that are already present and providing luxuries Section 5.1 Vanishing Species pg.111-120 Chase Upshaw Biological Diversity Biodiversity- refers to the variety of species in a specific area The simplest and most common measure of biodiversity is the number of different species that live in a certain area Where is biodiversity found? Biodiversity increases as you move toward the equator Tropical regions contain 2/3 of all land species on Earth Richest environments for biodiversity are usually the warmest places Studying biodiversity Study of islands in 1960; testing the development of biodiversity on islands Used islands off the coast of Florida Removed the organisms and observed which ones came back first Importance of Biodiversity You might go to a place in nature to relax, think, or get inspiration for songs, paintings, photographs, and literature Importance to nature All living things are interdependent; they rely on others to survive The loss of a population may greatly affect the entire ecosystem Biodiversity brings stability Ecosystems are stable if their biodiversity is maintained A change in species can destabilize More difficult for disease to spread Importance to people Humans depend on other organisms for their needs Plants for oxygen and food Animals for food Biodiversity could help breeders produce additional food crops Cross breeding to get the best characteristics Maintain health of humans Penicillium bacteria is used to make penicillin Loss of Biodiversity Extinction- the disappearance of a species when the last of its members dies Background extinction is responsible for 1 out of every 1,000,000 extinctions, but the regular extinction rate is higher than that Extinction is due to: Expanding human population Habitat loss Land exploitation Endangered species- when a species numbers become so low that extinction is possible Threatened species- when the population of a species is likely to become endangered Threats to Biodiversity Changes to habitats can threaten organisms with extinction Habitat loss One of the biggest reasons for decline of biodiversity is habitat loss The soil in the Amazon has very little nutrient supply Coral reefs are similar to tropical rain forests in biodiversity Habitat fragmentation Habitat fragmentation- the separation of wilderness areas from other wilderness areas Can contribute to: Increased extinction of local species Disruption of ecological processes New opportunities for invasions by introduced or exotic species Increased risk of fire Change in local climate Decreases biodiversity Edge Effect The edge of a habitat or ecosystem is where one habitat or ecosystem meets another Edge effect- the different conditions along the boundaries of an ecosystem Greater biodiversity because different habitats with different species are brought together Animals are brought together Habitat degradation Habitat degradation- the damage to a habitat by pollution Three types of pollution- air, water, and land pollution Acid precipitation- rain, snow, sleet, and fog with low pH values or levels Water vapor combines with air pollution to form acid precipitation Ozone layer- the region that absorbs some of the ultraviolet waves striking the atmosphere reducing the ultraviolet radiation reaching the Earth’s surface Water pollution Degrades aquatic habitats in streams, rivers, lakes, and oceans Detergents, heavy metals, and industrial chemicals in runoff affect aquatic habitats; excess fertilizers and animal wastes can also have an impact in degrading aquatic habitats Land pollution The average person produces about 1.8 kg of solid waste daily and about 657 kg each year Hard to decompose wastes in landfills are an example of pollution Pesticides on crops is another example of land pollution Exotic species People sometimes introduce a new species into an ecosystem, either intentionally or unintentionally These species are called exotic species They can cause problems for the native species in the area Exotic species- nonnative species in an area; may take over niches of native species in an area and eventually replace them Section 5.2 Conservation of Biodiversity pg.121-125 Conservation Biology Conservation biology- the study and implementation of methods to protect biodiversity Strategies are based on principles of ecology Includes natural resource conservation and species conservation; even soil Natural resources are those parts of the environment that are useful or necessary for living organisms Includes sunlight, water, air, and plant and animal resources Legal protections of species The U.S. Endangered Species Act became law in 1973, in response to concern about species extinction The law made it illegal to harm any species on the endangered or threatened species lists and for federal agencies to fund any project that would harm organisms on these lists The Convention on International Trade in Endangered Species has established lists of species for which international trade is prohibited Preserving habitats Creation of natural preserves and parks First U.S. national park, Yellowstone, was established in 1872 Protects the environment and provides habitats for many organisms Habitat corridors Best strategy is to protect the largest area possible Habitat corridors- protected strips of land that allow the migration of organisms from one wilderness area to another Working with people Rangers manage national parks and ensure the protection of organisms Sustainable use- a philosophy that strives to enable people to use natural resources in ways that will benefit them and maintain the ecosystem Reintroduction and species preservation programs Reintroduction programs- programs that release organisms into an area where their species once lived in hopes of reestablishing naturally reproducing populations Most successful reintroductions occur when organisms are taken from an area in the wild and transported to a new suitable habitat Captivity Some species no longer exist in the wild, but a small number of individual organisms are maintained by humans Captivity- an organism that is held by people Protecting plant species Best way to protect a plant species is to allow it to exist in a natural ecosystem Another way is storing the seeds in seed banks Reintroductions of captive animals is more difficult than the reintroductions of plants Keeping animals in captivity, with enough space, adequate care, and proper food is expensive Animals kept in captivity may lose the necessary behaviors to survive and reproduce in the wild