Lecture 13 - Ecology Flashcards
Definition of ecology
scientific investigation of interactions among organisms and between organisms and their physical environment
generates knowledge about the complex interrelations in the natural world
- not environmentalism
- even small organisms have an effect
Dung Beetle example
- settlers from britain btought cattle to australia
- didnt bring right kind of dung beetle
- normally consume and break down dun
- without this, pastures become unusable for grazing
- bush fly population exploded
- parasitic infections in cattle increased
- imported correct dung beetle to solve problem
Climate
- determines the kind of organisms that can survive and reproduce in a particular place
- energy from sun is main determinant
Climate vs weather
weather: the short term state of atmospheric conditions at a particular place in time
climate: average atmospheric conditions and their extent of variation at a particular place over a long span of time
Solar energy and latitude
Equator:
- sunlight is perpendicular
- most energy
Poles:
- at an angle
- less intense
- higher latitudes experience greater variation in day length and angle of solar energy over the course of a year, leading to more seasonal variation in temp
Solar energy and Air circulation –> rainfall
- when air is warmed, it expands and rises
- as it rises it cools
- cool air cannot hold as much moisture as warm air
- cooling air releases moisture in the form of precipitation
- warmest at equator, most precipitation in rain forests - as air rises it is replaced by air from the north and south
- draws in air from the region around 30 degrees latitude - cool dry air descends into the region
- earths great deserts - at about 60 degrees latitude air rises again
–> creates wind patterns
Wind pattern
- cyclic movement of air masses rising and falling contribute to wind (north and south)
- roatation of earth on its axis also contributes to prevailing winds (winds deflected est or west)
- velocity of rotation is fastest at the equator, where the diameter is the greatest
- air mass moving towards the equator is rotating slower than the earth beneath it - wind blows to the west
(ex: tradewinds columbus used to sail to americas) - air mass moving towards the poles is rotating faster than the earth beneath it - wind blows to the east
(ex: westerlies which cause most us weather to move from west to east)
Ocean currents
Air circulation patterns drive currents:
- ex: westerlies and tradewinds blow in opposite directions
- continents prevent water from circling the globe
- water is pushed together at equator, where it moves westward until it reaches land and then divides
- clockwise in N. hemisphere, counter-clockwise in S. hemisphere
Currents affect climate:
- poleward movement of water that has warmed in the tropics transfers large amounts of heat to higher latitudes
- ex: gulf stream to europe
Role of local topography
- major topographic features such as mountains or large lakes have regional effects on temperature and precipitation
- when winds bring air masses into contact w/mountain range, air rises to pass over
- -> cools as it rises
- -> clouds frequently form on windward side and release rain and snow
On leeward side (opposite from winds), now dry air descends, warms, and picks up moisture
- -> little rain and arid condition
- -> rain shadow
Biomes
Combination of sun intensity, wind patterns, ocean currents –> many distinct environments
Environment characterized by:
- climactic and geographic attributes
- ecologically similar organisms (especially plants)
animals in similar biomes often share many physiological, morphological and behavioral adaptatons
distribution determined largely by temperature and rainfall
Tundra
Winter is cold and long, summer is cool and short. Little precipitation
Arctic: Near poles
- vegetation is low-growing perennial plants
- underlain by permafrost (soil with permanently frozen water)
- usually wet cause water cannot drain through permafrost
Alpine: High elevations
- not underlain by permafrost
- low growing shrubs and grasses
*most animals either summer migrants or dormant for much of the year, thick fur
Boreal and temperate evergreen forest
Winter is cold, dry and long, summer is mild and humid
- latitudes below arctic tundra and elevations below alpine tundra
- short summer favors trees with evergreen leaves that are ready to photosynthesize as soon as temperatures warm
- conifer trees and shrubs
- animals: moose, hares, rodents and birds that eat conifer seeds
temperate and deciduous forest
Winter is cold and snowy, summer is warm and moist
- many types of deciduous trees (lose leaves in winter, shrub layer
- temperatures fluctuate dramatically between summer and winter
- precipitation is evenly distributed through the year
- many types of animals
- some migrate in winter, other have massive fat stores and hibernate
temperate grasslands
- Relatively dry most of the year, winter cold and dry, summer is warm and wetter
- vegetation - mostly grasses, few trees
- animals - grazing herds
- plants adapted to grazing and fire (energy underground and sprout quickly after being burned or grazed)
- topsoil is usually righ and deep, good for crops especially corn and wheat
hot desert
- around 30 latitude
- Hot and dry: winter is very warm and dry, summer is very hot and dry (but slightly less dry)
- plants are structured to conserve water
- small animals are inactive during hottest part of the day- can burrow underground
- mammals have physiological conditions for conserving water (ex: high concentrated urine)
- -> many require no water beyond what they can extract from carbohydrates in food
cold desert
high and dry: mid to high latitudes (rain shadows of mountain ranges)
- seasonal changes in temperature are large
- winter is cold and very dry
- summer is much warmer, still dry
- few species of low-growing shrubs
- animals tend to be seed-eating birds, ants, rodents
- many animals burrow
chaparral
Warm (mild), dry summers and wet, cool (mild) winters
- found in mid-latitudes on western sides of continent where cool ocean currents flow offshore
- low growing shrubs and trees with tough evergreen leaves that conserve water
- many small rodents
- animals burrow to avoid mid-day heat and forage at night
Tropical savannah
Winter is mild and dry, summer is very wet but not much warmer than winter (mild temps)
- latitudes in between the hot deserts and the equator
- many plants similar to those found in hot deserts
- spiny shrubs and small trees
- expanses of grasses with scattered individual trees
- acacia tree common
- herds of grazing and browsing mammals and then large carnivores that prey on them
- if not grazed, browsed or burned, reverts to dense thorn forest
tropical deciduous forest
Winter is very hot and dry, summer very hot and wet
- as length of rainy season increases closer to equator, tropical deciduous forest replaces thorn forest
- taller trees and fewer succulents
- support a much greater number of plant and animal species
- “nectar corridor” = many flowering plants
- fertile soil for the tropics area
tropical evergreen forest
rainforest- warm and rainy all year
- near equator
- most species rich of all biomes
- forests, cover <2% of earths surface, but are home to over half of all known species
Population Ecology
vs
Community Ecology
Regulation of a population of one species
vs
How populations of different species interact with and influence one another
Population
- individuals of a species that interact with one another within a given area at a particular time
- groups of individuals that interact in space in time have characteristics that individuals do not
- have a characteristic dispersion pattern (spatial distribution)
- have a characteristic age structure
Population density
- the number of individuals per unit of area or volume
- births and immigration vs deaths and emigration
Population dynamics
- the patterns and processes of change in populations
Measuring population densities
- in most species it is impossible to accurately count all individuals
- pop per unit is estimated by samples
SEDENTARY organisms
- count the individuals in a sample of representative locations
- extrapolate the counts to the entire geographic range of populations
MOBILE organisms
- capture, mark, release
- allow time for marked individuals ot mixed with unmarked
- capture another sample
- determine what proportion in new sample has the mark
Life Tables
Track demographic events and rate at which they occur in a population
births, deaths, immigration, emigration
Cohort life table: Survivorship
- start with a group of individuals born at the same time and track their deaths until no individuals from that cohort remain alive
Calculate the survivorhip and mortality:
Survivorship: proportion of the original coort that survived to reach that age class
mortality: proportion of individuals in each class that die before reaching the next age class
Cohort life table: Fecundity
- cohort life tables also used to track the degree to which individuals in different age categories contribute to reproduction
- track the number of offspring produced by each female during each time period
Fecundity: the average number of offspring per female
- allows scientists to estimate a populations potential for growth
- vary greatly among species
- # of offspring they can reproduce
- timing of reproduction
Survivorship Curve
- mortality data from a life table can be used to plot a survivorship curve
- classified by the pattern the population displays
x= age y= survivorship
Types of survivorship curves
Type I: Physiological
- organisms that experience high overall survivorship through adulthood (such as humans)
- parental care and low fecundity
Type II: ecological
- organisms faced with a constraint risk of mortality at all ages (such as birds)
Type III:
- organisms that experience low juvenile survivorship (such as insects and annual plants)
- many offspring but little or no parental care
Exponential growth
as the number of individuals in a population increases, the number of new individuals added per unit of time accelerates
conditions for populations to grow exponentially
*short period of time
- unlimited resources
- no predators
- favorable climate