2.1: Species and Populations

significant ideas 2.1

1) a species interacts with its abiotic and biotic environments; its niche is described by these interactions

2) populations change and respond to interactions with the environment

3) a system has a carrying capacity for a given species

ecology

the study of the living (biotic) and non-living (abiotic) parts that interact within an ecosystem

abiotic factors

non-living, physical factors in an environment (rocks, sunlight, wind, etc)

biotic factors

living-factors in an environment (plants, animals)

species

group of same type of organisms which can mate and produce fertile offspring

mules are not species because they have 63 chromosomes which cannot evenly divide, not sterile = not a species

keystone species

species that are crucial to the maintenance of their ecosystem/vital in determining the nature and structure of the entire ecosystem (wolves in yellowstone, sea otters in kelp beds)

habitat

where an organism lives (must provide food, water, and shelter) (address - sea ice for polar bears)

niche

particular set of abiotic and biotic conditions & resources to which an organism or population responds encompasses both physical/environmental conditions it requires and the interactions with other species (profession - tigers = apex predators which keep herbavore populations controlled)

levels of organisation

species, population, community, ecosystem, biome, biosphere

binomial nomenclature

scientific names

rules:

• two parts: Genus species

• always underlined or italicized

• Genus capitalized, species not

niche partitioning

species occupy different areas (like how warbler species prefer to feed at different heights on a tree, therefore reducing competiton)

fundamental vs realized niche

* no 2 species can have the same ecological niche in the same place at the same time

fundamental niche = the entire range of conditions in which a species could live

realized niche = the actual conditions under which the species lives (usually due to competition)

• Joseph Connell’s experiment: Semibalaus barnacles were abundant in mid to low intertidal zones, Chthamalus in the upper area. Removing Chthamalus, no Semibalanus repalces it (because their fundamental and realized niche were the same). When he removed Semibalanus, Chthamalus replaced it b/c Semibalanus was a better competitor, and the fundamental niche of Chthamalus was much bigger than its realized one)

intraspecific vs interspecific competition

intraspecific = competition for resources between organisms of same species (lots of mating competition, occurs b/c of overpopulation)

interspecific = competition for resources between 2+ species (no mating competition, occurs b/c of lack of physical resources)

population

group of same species in a specific range (interbreeding and interacting)

• when populations are separated geographically, interbreeding stops and new species are formed

• population dynamics: the study of the change in populations over time

predation

preying of one animal on others

herbivory

consumption of plant material by animals

parasitism

interaction where one species benefits and the other is harmed

mutualism

both species benefit

commensalism

one species benefits, the other is not harmed nor benefited

r-select species

species that produce large numbers of offspring, no maternal instinct, short lifespans, small in size, large in density

k-select species

species with longer lifespans, bigger in size, overlapping generations, longer gestation so less young, more energy, longer to reach maturity, maternal instinct

j-curves

• no limiting factors → exponential growth

• not realistic for most populations

• boom & bust pattern (growth then sudden collapse due to intro of limiting factor)

• population usually exceeds carrying capacity (the max # of organisms of a single species that an ecosystem can support) → overshoot then dieback

• typical with r-select species

s-curves

• first exponential growth phase (abundant food, space, light)

• then transitional phase due to competition (intra)

• population reaches carrying capacity and slows

• represents logistic growth

• environmental resistance: when exponential growth slows until carrying capacity is reached

• in reality, it won’t exactly flatline, but fluctuate around the carrying capacity (an example of a negative feedback loop)

types of limiting factors

biotic: food, predation, disease, parasitism, invasive species, competition

abiotic: water, living space, global warming

both: habitat destruction, shelter, soil