EQ: How does succession lead to a climax community?

SUCCESSION

Succession•P

rimary Succession• Occurs in places where life has never existed before• There is no soil!• Pioneer species are the first species to arrive• Often moss or lichen (Freddy Fungus took a LICHEN to Alice Algae and now

their relationship is on the rocks) • Clings to the rocks and breaks it down to create soil

•Secondary Succession• Occurs where life has previously existed but was wiped out for some reason• SOIL IS AVAILABLE!

•Both types of succession end in a stable climax community

http://www.nps.gov/media/photo/gallery.htm?id=3EB5B850-155D-4519-3EC97FCF1D50262A

EQ: How do populations impact the environment? How does the environment impact populations?

POPULATION GROWTH

Exponential Growth

•The simplest form of population growth is exponential• Population growth that expands faster and faster• 2 becomes 4 becomes 8 becomes 16 becomes 32…• This does not realistically occur

Logistical Growth

•Growth in which there are a series of phases and ends in a steady state where the number of individuals leaving the population is equal to the number of individuals entering the population

Points of a Logistical Growth Curve

•A : The species is first introduced to the environment• Growth is slow

•B : A period of exponential growth occurs

•C : Growth slows

•D : population growth reaches a peak – the maximum number of individuals that can survive in the environment

•E : Steady state

Terms•Growth occurs when birth rate is higher than death rate•Steady state is when there is no population growth on average•Carrying capacity is the average number of individuals in a population at steady state

Limits to growth•T

here are two types of limits to population growth – density dependant and density independent.

•Density dependant means that the extent to which a factor limits population growth is dependant on the amount of individuals already in the population

•Density independent means that the factor limits population growth regardless of the number of individuals already in the population.

•A limiting resource is something that each organism needs to live and which is in limited supply• Food is such a resource

Density Dependant Factors

•Competition• If there is only a limited amount of resources available to the individuals they will compete for them• Only the strongest individuals in a large population will get use of the resources and be able to have young• Called intraspecific competition if it occurs within a species

Density Dependant Factors•P

redation• The act of one organism eating another• The organism doing the eating is the predator and the

organism being eaten is the prey

• Causes a decrease in the prey population• If the predators don’t eat too many individuals than birthrate

can replace those that die keeping the population in steady state• If the predation is intense the population decreases

• The number of prey and the number of predators are inter related – if the predators eat all the prey they will begin to starve to death; if the predators are scarce than the prey can have a jump in population

Predator – Prey Relationships•P

rey are introduced to the environment – multiply and are happy

•Predator population increases because of plentiful prey

•Prey population decreases because of plentiful predators

•Predators population decreases because of lack of prey

•Prey population increases because predator population decreased

Good News•P

redators often have a lot of variety in their diet and therefore the fluctuations between predator and prey interactions are not usually this dramatic

•Some predators only take a bite out of the prey allowing it to survive another day

•Most prey items usually have some defense against being eaten

Density Dependant Factors•P

arasitism• One organism lives on or in another organism eventually causing harm to the host• Very few marine organisms are parasite free• Parasites can be spread among individuals so the larger the population the greater risk for any one individual to die of a parasite

Density Dependant Factors•C

rowding and Stress• The more individuals in a population the faster they use up the limited resources available to them• Eventually there is not enough resources left to support any more individuals so the population levels off• The more crowded a population the more stress comes into play weakening immune systems and making individuals more prone to illness

Density Independent Factors

•Climate is the main density independent factor that affects organisms• El Nino which raises or lowers the water temperature can affect food sources

Geographic Distribution•M

ain factor in determining population size

•Where a population is located across the Earth