* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Download Species and Populations
Document related concepts
Species and Populations Significant ideas A species interacts with its abiotic and biotic environments, and its niche is described by these interactions. Populations change and respond to interactions with the environment. Any system has a carrying capacity for a given species Species A species is a group of organisms that share common characteristics and that interbreed to produce fertile offspring. Humans, Giraffes, Pine Trees Species are given scientific name with genus and then species (in italics) Humans Homo sapiens Wolf Canus lupus Populations and Habitats Population: A group of individuals of the same species living in the same area at the same time. Able to interbreed Snails in two different ponds may breed with only snails in each respective pond. Populations can be separated by geography and eventually stop interbreeding Form a new species this way. Habitat: The environment where a species normally lives. Includes Abiotic and Biotic Factors Examples of habitats? Abiotic Vs. Biotic Abiotic (non-living) Factors Atmosphere/Sunlight Climate Soil structure and chemistry Water chemistry Seasonality Level of Pollutants Biotic (living) Factors Producers Consumers Decomposers Predation Parasitism Mutualism Disease Competition Community A group of populations living and interacting with each other in a common habitat. Example: Tropical Rainforest- plants, animals, bacteria, and fungi. Ecosystem A community of interdependent organisms and the abiotic (physical) environment which they inhabit. As small as a drop of rainwater to as large as an ocean All ecosystems are affected by humans Niche An organisms “occupation” or “job”. Its relationship to its food and predators. Describes the particular set of abiotic and biotic conditions and resources to which an organism or population responds Example: Small fish in a coral reef share the same habitat, but each species has a different niche. Each population has a different “job” based on its shape, size, color, behavior, and feeding habits. Population Growth and Changes Exponential or Geometric Growth: Occurs when no limiting factors slowing growth Usually produces a J-Curve Examples? Bacteria in a petri dish Humans Limiting Factors: Reduce or stop population growth Density-Dependent Density-Independent Density-dependent limiting factors: biotic factors that tend to increase with increasing population size. Density-Independent limiting factors: tend to be abiotic. Not related to population density. Act as negative feedbacks that lead to stability or regulation of a population Internal factors act within a species: limited food supply, limited territory, limited fertility. External factors act between species: Predation, disease. Would a higher population density affect predator-prey relationships? How? What about spread of disease? Examples: weather, climate, volcanic eruptions, floods What would be a densityindependent factor for humans? Lynx and Snowshoe Hare Density-dependent limiting factor. Internal or external? Population Curves J-Curve S-Curve S-Curve reality J-Curve Reality Population Curves J-Curve Boom and Bust pattern Population grows exponentially at first and then suddenly collapses Collapses are called “diebacks.” Often the population exceeds carrying capacity before the dieback occurs S-Curve Start with exponential growth, however above a certain population size the growth rate slows down gradually until it’s constant. Growth slows down more in larger populations. Density-independent or dependent? Density independent or dependent? Typical of microbes, invertebrates, fish, and small mammals Typical of large mammals and humans Carrying Capacity Carrying Capacity (K): Maximum population size supported by ecosystem. Based on the two curves we just looked at, what happens if a population exceeds its carrying capacity? Do you think humans have or ever will reach carrying capacity? What evidence would support humans reaching carrying capacity? K- and r-strategists: Reproductive strategies K and r are two variables that determine the shape of the population growth curve. r = growth rate of the population K = carrying capacity K-Selected Species r-Selected Species Have small numbers of offspring but invest large amounts of energy in parental care. Have extremely large numbers of offspring, but invest little or no time raising them. Most offspring survive, long lives Reproduce quickly, but short lived Examples? Colonize new habitats rapidly Humans Large mammals Good competitors and population is usually close to carrying capacity Can outcompete r-strategists in good conditions Usually exceed carrying capacity and populations collapse. Predominate in unstable ecosystems Examples? Invertebrates and fish What about us? …carrying capacity is determined jointly by human choices and natural constraints. Consequently, the question, how many people can the Earth support, does not have a single numerical answer, now or ever. Human choices about the Earth's human carrying capacity are constrained by facts of nature which we understand poorly. So any estimates of human carrying capacity are only conditional on future human choices and natural events." Joel Cohen Survivorship Curves Shows the fate of a group of individuals of a species. Type 1-K-strategists Type 2- r-strategists Type 3- Rare. Represents species that has equal chance of dying at any age.