Unit 4

• ecology


  the study of interactions among and between organisms and their nonliving environment
• population


  a group of organisms of the same species living and interacting in a particular area
• community


  interacting populations of different species in a defined habitat
• ecosystem


  all the living and nonliving components of an environment and how they interact
• dispersion pattern


  the way organisms are distributed in a geographic space
• random dispersion


  organisms are spread out randomly with no order
• clustered dispersion


  occurs when resources are unevenly distributed throughout an area
• uniform dispersion


  individuals keep apart at regular distances due to territorial behavior
• growth rate


  the difference between the birth rate and the death rate in a population
• immigration


  the movements of individuals into a population
• emigration


  the movement of individuals out of a population
• exponential growth


  the unrestricted growth of a population increasing at a constant growth rate
• habitat


  the physical environment where an organism lives and to which it is adapted
• The two types of population growth are logistic growth and exponential growth
• logistic growth


  a pattern of growth that starts off fast and levels off as the population reaches the carrying capacity
• carrying capacity


  the maximum population size that a given environment can support with its resources
• population density


  the number of organisms per unit area
• density-dependent factor


  a factor whose influence depends on the number and crowding of individuals in a population
• abiotic


  the nonliving components of an environment
• density-independent factor


  a factor whose influence DOES NOT depend on the number of individuals
• food chain


  represents a linked series of feeding relationships in a community
• predator


  an organism that feeds on other organisms
• herbivore


  organisms that feed on plants, which may or may not kill the plant
• trophic level


  feeding levels based on positions in a food chain
• food webs


  represents a complex interconnection of feeding relationships in a community
• symbiosis


  a situation in which two different organisms live together, often interdependently
• mutualism


  both species benefit from the interaction
• parasitism


  one species benefits at the harm and cost of the other
• commensalism


  one species benefits and the other isn’t harmed or benefited
• niche


  the space, environmental conditions, and resources that a species needs to survive and reproduce
• Competitive Exclusion Principle


  in theory, no two species can occupy the same niche
• resource partitioning


  in reality, species generally don’t occupy the exact same niche
• keystone species


  a species on which other species depend upon, and whose removal has a dramatic impact on the community
• pistil


  the female parts of the flower
• stamen


  the male parts of the flower
• colony collapse disorder


  all worker bees abandon a hive, leaving developing bees to die
• Colony collapse disorder may occur due to stress, pesticides, parasites, and viruses.
• pollen


  small, thick-walled plant structures that contain cells that develop into sperm
• pollination


  the transfer of pollen from male to female plant structures for fertilization
• producers


  autotrophs that obtain energy from the sun and form the base of the food chain