Understanding Populations Chapter 8 Environmental Science

Population All the members of a species living in the same place at the same time Organisms from the same population breed with each other, usually not other populations Three ways to describe populations Size Density Number of individuals per unit area or volume Dispersion Distribution or arrangement of individuals within a given amount of space

How does a population grow? Growth rate Change in the size of a population over a given period of time Change in population size Birth rateDeath rate = -

How fast can a population grow? Reproductive potential Maximum number of offspring that each member of a population can produce Some species have a higher reproductive rate than others Biotic potential Fastest rate that a population can grow Reproductive potential increases when individuals: Produce more offspring at a time Reproduce more often Reproduce earlier in life  Bacteria (short generation time), humans (longer generation time)

Exponential Growth When a population grows faster and faster Example: Dog gives birth to 6 puppies  Next generation – 18 puppies and so on Occurs in nature when: Plenty of food and space No competition or predators

What limits population growth? Carrying capacity The maximum population that the ecosystem can support indefinitely Populations may go over this number Carrying capacity can be estimated, not exact

What limits population growth? Resource limits Limiting resource A resource that is being consumed at the same rate it is being produced Example: plant growth limited by…..  Water  Sunlight  Mineral nutrients Supply of the most limiting resource determines the carrying capacity of an ecosystem

What limits population growth? Competition within a population Species in a population use the same resources in the same ways (ex. Food) Indirect competition Competing for their territory  Area defended by one or more individuals against others Territories are valuable to an organism  Space  Shelter  Food  Breeding sites

Growth Rate Math Practice Page 201 Worksheet

Population Regulation Density dependent Deaths occur quickly in crowded populations  Limited resources  Predation  Disease Density independent Portion of population will die regardless of density Possible causes  Severe weather  Natural disasters

Assignment Page 202 Section 1 Review # 2-5

How Species Interact with Each Other Niche Unique role of a species within an ecosystem Includes: Species’ physical home Environmental factors necessary for survival Interactions with other organisms Different from habitat Habitat is only a location Niche is a pattern of how the habitat is used Can be thought of as a job in an ecosystem

Ways Species Interact Competition Different individuals or populations attempt to use the same limited resource Can occur within a species or between a species Indirect competition Example – one insect feeds on a plant during the day and another insect feeds on the same plant at night Adaptations can occur over time to decrease competition  Using less of a niche than they are capable of using  Similar species will divide up the niche to “share space”

Ways Species Interact Predation Predator Feeds on another organism Prey Organism that is fed upon Organisms can be a predator and the prey Some predators will only eat specific types of prey

Ways Species Interact Parasitism Parasite Organism that lives in and feeds on another organism Host Organism the parasite takes its nourishment from Examples of parasites Ticks Fleas Tapeworms

Ways Species Interact Mutualism Close relationship between two organisms where both benefit Example – bacteria in your intestines and you Commensalism Relationship where one species benefits and the other is neither helped nor harmed Example – Birds nesting in trees (causing no harm to the tree)

Ways Species Interact Symbiosis Relationship where two organisms live in close association Coevolution Relationships may coevolve over time Can reduce the harm to an organism Can increase the benefit to an organism

Assignment Page 209 Section 2 Review # 1-5

Chapter 8 Review Questions Pages # 5-18, 21-23, 25, 31