Ecology The study of how organisms interact with each other and their environment

Key Elements of the Environment Temperature – most organisms require a narrow range (humans excluded) Water – very important, much more diversity in rainforest than in desert Sunlight – where almost all energy originates from Soil – pH, minerals, nitrogen, phosphorus affect the ability of plants to grow

Population properties Population size – number of individuals Population density – number of individuals in a given unit Los Angeles – 7544 people/square mile South Sioux City, NE – 2725 people/square mile Manila, Philippines – 111,576 people/square mile New York City – 27,012 people/square mile Population dispersion clumped uniform random

Population growth Population at current time = population from past time + births during that time – deaths during that time + immigration – emigration Simulation of population growth – start off with 10 people (5 couples) – each couple has 4 kids How many offspring? - 20 20 children become adults and each couple has 4 kids How many offspring? – 40 Doubles each generation – so let’s draw a graph

Population growth Exponential growth – the larger the population, the more it will grow Eventually this has to stop Space Availability of resources Carrying capacity – the max population This type of growth is called logistic growth (sometimes called a sigmoid curve)

Factors that influence population density Density-independent events Severe weather (floods, drought, etc.) Severe geological disturbances (volcanoes, earthquakes, etc.) Density-dependent events Aggressive behaviors (defending territory) Emigration

Maximizing population productivity Demand for fish has increased due to general health benefits and increase in global population Overharvesting has caused population decline in wild salmon Salmon farms have helped alleviate the problems of overharvesting Farms have negative health and ecological impact Toxins in fish Fish lice and viruses are becoming common if farmed salmon, which are passing them on to wild salmon overharvesting Wasting resources Maximum sustainable yield

Demography The study of populations using statistics Cohort – A group of individuals that are the same age Fecundity – Number of offspring produced in a standard time (for example, a year) Mortality – The number of individuals that die in that time Proportion of males to females is called the sex ratio

Survivorship curve Type I – Most live a long time, then suddenly die Type II – constantly die off Type III – many die off young, the ones that survive live for quite some time

Community and Ecosystem Community - all the species in a given area Ecosystem – all the species and all the non-living components in a given area

The Niche and Competition Niche – all the ways in which an organism uses its habitat Habitat – the place where an organism lives Competition – when two organisms attempt to use the same resource Interspecific – between two different species Intraspecific – between the same species

Fundamental Niche vs. Realized Niche Fundamental Niche – where a given species is ABLE to live Realized Niche – where a given species actually lives because of competition

Competition Competitive exclusion - If two species are competing for the same resource, the one that uses it more efficiently will out grow the other Population Time P. Bursaria grown separately No two species can occupy the same niche if resources are limited. If two species coexist… Resources are not limited They do not occupy the same niche

Resource partitioning Competition between two species is rare in nature because of 2 reasons: One would outcompete OR A new niche would be formed by dividing up resources – resource partitioning Sympatric – closely related species that divide up resources – must live close to each other Allopatric – closely related species that do not divide up resources – so usually do not live close to one another Allopatric species look more alike than sympatric species – called character displacement

Character Displacement Character displacement is not the same as disruptive selection

Coevolution Symbiosis – two organisms that live together and whose existence is altered because of this relationship Mutualism – both benefit Commensalism – one benefits, other is unharmed Parasitism – one benefits, other is harmed Sometimes parasitism can be considered a predator-prey relationship

Predator/Prey cycles Predation – the consuming of one organism by another Predator – the one doing the eating Prey – the one being eaten

Defense against predators Plants Thorns Spikes Prickles Chemicals (pungent tastes usually associated with toxicity) Many others Animals Poisons Warning coloration Camouflage Speed

Mimicry – a type of defense Batesian mimicry – non-harmful organism mimics the look of a harmful organism Mullerian mimicry – similar pattern development between harmful organisms Self-mimicry – one body part looks like another body part Mullerian Batesian Mullerian poisonous Non-poisonous venomous

Ecological succession Succession – more complex communities replace simpler ones as time goes on Primary Succession – occurs on a substrate that never had life prior Examples: volcanoes, rocks, lakes left by glaciers Secondary Succession – occurs on a substrate that had life prior, but was almost completely wiped out Deforestation, flood, fire