Unit 3: Populations

• Habitat diversity: the variety of habitats that exist in a given ecosystem
• Specialist species: found in one habitat; species that only live under a narrow range of biotic and abiotic factors
• Generalist species: found across multiple habitats; species that can live under a wide range of biotic and abiotic factors
• Native species: species that live in their historical range - typically where they've lived for thousands of millions of years
• Alien/exotic species: species that live outside their historical range
• Invasive species: when alien species spread rapidly across large areas (ex: kudzu vine and zebra mussel)
• Hunting, fishing, other forms of harvesting: the most direct human influences on wild plants and animals
• Over-harvesting: when individuals are removed at a rate faster than the population can replace them (can cause extinction)
• Keystone species: a species that plays a role in its community that is far more important than its relative abundance might suggest
• Predator mediated competition: indirect negative interaction between two prey species mediated by a shared predator
• Ecosystem engineers: a keystone species that creates or maintains a habitat for other species
• Ecological succession: the predictable replacement of one group of species by another group of species over time
• Primary succession: occurs on surfaces that are initially devoid of soil
• Secondary succession: occurs in areas that have been disturbed but have not lost their soil
• Pioneer species: a species with the ability to colonize new areas rapidly and grow well in full sunshine
• Competition: the struggle of individuals to obtain a shared limited resource
• Realized niche: the range of biotic and abiotic conditions under which a species actually lives
• When 2 species have the same realized niche: one species will perform better and will drive the other to extinction
• Anthropology: pollution or environmental change originating in human activity
• Competition exclusion principle: 2 species competing for the same limiting resource cannot coexist
• Resource partitioning: when two species evolve to divide a resource based on differences in their behavior or morphology
• Spatial resource partitioning: species live in different parts of the same place
• Morphological resource partitioning: species lower competition by evolving in body and shape
• Temporal resource partitioning: species utilize the same resource at different times to reduce competition
• Predation: the use of one species as a resource by another species
• Parasitoids: organisms that lay eggs inside other organisms
• Symbiosis: a close and long-term interaction between 2 species in an ecosystem
• Mutualism: (ex: bees and flowering plants; clownfish and sea anemones)
• Density-dependent factor: a factor that influences an individuals probability of survival and reproduction in a manner that depends on the size of population
• Density-dependent factor examples:


  • competition for resources
  • predation
  • disease
  • parasitism
• Density-independent factor: a factor that has the same effect on an individual's probability of survival and reproduction at any population size
• Density-independent factor examples:


  • natural disasters
  • climate change
  • pollution
  • habitat destruction
• Population growth model: mathematical equation that can be used to predict population size at any moment in time
• Population/Intrinsic growth rate: the number of offsprings an individual can produce in a given time period, minus the deaths of the individual or its offspring during the same period
• Exponential growth model: a model that estimates a populations future size after a given period of time based on the biotic potential and the number of reproducing individuals currently in the population
• J-shaped curve: the curve of the exponential growth model when graphed
• Biotic potential: maximum potential for population growth under ideal conditions, with unlimited resources available (r)
• Logistic growth model: a model the describes a population whose growth is initially exponential, but slows as the potential approaches the carrying capacity of the environment
• S-shaped curve: the curve of the logistic growth model when graphed
• Carrying capacity: the limit to the number of individuals that can be supported by an existing habitat or ecosystem (k)