3. What is a Population? All the members of a species living in the same place at the same time. Density – the number of individuals per unit area or volume. Number of bass per cubic meter of water in a lake

4. How Does a Population Grow? Growth rate – a change in the size of a population over a given period of time. Growth rate = birth rate – death rate

5. How Fast Can a Population Grow? Reproductive Potential – the maximum number of offspring that each member of the population can produce. Bacteria populations can reproduce in only a few hours Human generation time is about 20 years – low reproductive potential Exponential Growth – growing faster and faster Occurs when populations have plenty of food and water, and have little or no competition or predators.

7. What Limits Population Growth? Carrying Capacity – the maximum population for a particular species that an ecosystem can support indefinitely. Resource Limits – a species reaches its carrying capacity when it consumes a particular natural resource at the same rate at which the ecosystem produces the resource. Then becomes a limiting resource Pribilof Islands – Alaska – Reindeer and lichens Competition Within a Population – members of a population use same resources in same ways, they will eventually compete for it. Territory – an area defended by one or more individuals against other individuals.

9. An Organism’s Niche The unique role of a species within an ecosystem. Physical home, environmental factors necessary for species’ survival, all species’ interactions with other organisms Habitat is just a location. Niche is an organism’s pattern of use of it’s habitat. American Bison – large grazing herbivores on American grasslands Kangaroos – Herbivores on Australian grasslands

10. Ways in Which Species Interact 1. Competition – different individuals or populations attempt to use the same limited resource. Indirect competition – never in direct contact Insect feeds on plant during day, other insect species feeds on plant at night Adaptations to Competition – competition reduced between species by dividing up the niche in time or space Niche restriction – when species uses less of the niche than it is capable of using. Barnacles

11. Ways in Which Species Interact 2. Predation – an organism that feeds on another organism is called a predator, and the organism being fed upon is the prey. Snakes eating mice, bats eating insects Predator-prey relationship

12. Ways in Which Species Interact 3. Parasitism Parasite – organism that lives in or on another organism and feeds on it Host – the organism the parasite take its nourishment from Ticks, Intestinal worms 4. Mutualism A close relationship between two species in which each species provides a benefit to the other E. coli in your intestines

13. Ways in Which Species Interact 5. Commensalism – a relationship in which one species benefits and the other species is neither harmed nor helped. Orchids and trees 6. Coevolution – a relationship in which two species live in close association Over time, species in close relationships may coevolve