population ecology-branch of biology that deals with the # s of a particular speices and the reasons those #s change over time.
- Demography-branch of sociology that studies yhe charateristics of human population
- -these feilds are important becaues at the root of all evn problems is the issue of population
Population density-often the size
of a population tells us little unless we know the boundaries.
therefore population density gives us the # of individuals of a speices per unit of area at a given time.
different env can sustain different population densities.
Population through time
-controlled primarly dased on 2 factors
Birth rate-reat wich individuals produce offspring (fertility rate)
Death rate-rate wich ppl die
Malthus and Carring capisity
-Thomas Mathus proposed ideas about population growth
-Population if unchecked will increase at a gemoritic rate(doubling) wile food supplies only grow at a arithmetic rate (1,2,3,ect)
Population is checked through natural processes (old age accidents war ect)
Therefore earth can only support so many ppl befor it reaches its carring capasity-maximum population that can be maintained w/o degradation of ecosystem.
Doubling time- amount of time it takes for population to double.
-can be estimated according to the rule of "70"
-70 divided by the growth rate %
-So if the global growth rate is 2%per yr the doublimg time is 70/2 or 35yrs World pop 6.8 billion
-Pre industrail birth and death rate are high pop. growing at moderate rate
-Transitional lower death rate cuz improvements in health care food and water supplies
-Industrial decline in birthrate (indistrilization process)
-Post industrial low birth rate and death rate, better educated ppl want smaller families.
to be able to pridict a fucher growth of a population, must know its age structure- distrubition of ppl by age.
Rapid, slow growth(stable), growth decline
pop is expected to reach 9 billion by 2050 and over 12 billion by 2150(double what we have today)
issues of sustainability have been raised.
Cultural infulances on over population
-culture values norms of society religous belifes gender issues moral and ethical belifes
-culture plays important role in determining # of offsring produced.
-some societies rely on children 5-14 to work (hight fertility rate developing cuntry)
-others expect children to attend school. (lower fretility rate developed country)
Population and worls hunger
-millions die each yr from hunger
-not because of failer of food production to keep up w pop.
-agriculture produces enough food for everyone if distrubuted evenly.
-inequalities between poor and rich
-somecountries w high fretility rate have the greatest food shortages, also are some of the poorest countries.
5 major terrestrial biomes
Temprate Deciduous forest
Found in middle latitudes of world
seasonal ecosystem-hot summer clod winter
contain brod-leaf trees, change color in fall and shed leaves in winter (maple oak)
Boral Forests (Taiga)
conifer (evergreen) trees, have long thin waxy needles. wax protects froom freezing and drying out.
located in colder regions just below tundra (north)
Areas w at least 6 mos of winter ex Alaska
Tropical Rainforest (south)
largest biomes in the world
Rainfall is usually 150in to over 300in per yr, located at the equator, high temp and humitity
So many spices of plants and animals only 1% have been studied
large rolling tarrains of grass flowers and herbs
found in the middle latitudes in the interiors of continents
-tall grass-humid env that are very wet
-short grasses- drier env w/ hotter summers and cloder winters
-mixed grasses-combo of both
low precipation fire and thin soil prevent development of forests (no trees)
extreemly cold climets, little precipitation lead to low bioligic diverstity
tree growth is hindered by low temp and short growing seasons
mainly composed of dwarf shrubs and grasses
-Artic tundra (north pole)
-Alpine tundra (mt areas)
-Antartic tundra (south pole)
Arctic tundra (N pole)
nothern hemisphere ebcircling the north pole and extending south to the coniferous forests of the tigia.
stark landscape frozen for much of the yr. covered by a layer of peramfrost.
Permafrost-soil at or below freezing for 2 or more yrs. over permafrost is a thin active layer that seasonaly thaws durring summer. Plant life can be supported in the active layer. Amount od permafrost depends on climate. 20% of the earth land masses is covered by permafrost, but decressing due to global warming.
Alpine tundra NO PERMAFROST
located on mts through out the world at high latitude where trees cant grow.they are usually at elevation of 10,000ft or more. just below the snow line of mt. lacks permafrost and is better drained than artic soils
Antartic tundra (S pole)
ANtartic and on several subantartic islands. often to cold and dry to support vegetation. most of the continent is covered by ice feilds. however somw portions of the continent have areas of rocky soil that supports plant life
Desert (not based on temp but on precipitation)
less than 10inc rain per yr.
Causes of natural deserts. found at 30 degrese N and S latitude. dry descending warm air masses. evaporation rates are high. Toporaghy and prevailing winds establish rain shadow effect. moister extracted on windward slopes of mt ranges. Desarts can be hot or cold
rolling grassland scattered w shrubs isolated trees(small and stunted) known as tropical grasslands-not enough precipation to support trees. found in Africa andIndia and northern part of S America. founf between the tropical rain forest and desart biomes
coast area that extends inland from the shore that is heavy influnced by action of waves. Waves generated by wind. size of waves affected by 3 factors:
length of time the wind blows over the water
fetch-distance along open water wich the wind blows.(bigger waves more energy)
Wave refraction- as waves approch shore part of the wave in shallow water slows down-due to the friction forces between bottom of wave and sea floor.Part of the wave in deep water continues at originls speed and causes the wave creat to refract (bend) waves dont land head on
longshore current- currwnt found off shore produced because waves bend.
littoral drift- movement of sand down beach carried by waves washing up, back, repeat.
Chaparral-smallest biome. costal biome created when cooler sea water meets a land mass with high average temp. lies 30-40 degrees above and below the equator. Winters are very mild and moist wile the summers are extreemly hot and dry. low precipation
Estuaries-area along a coastline where rivers flow into an ocean. fresh water mixes w salt water to create brackish water. certian speices have adapted to live in these areas. largest estuaries Chesapake Bay Maryland
Wetlands- transitional area between treesertail and aquatic ecosystems. Area of land whose soil is saturated w water permintally or seasonally. Often has standing water covering land include swamps marshes and blogs
Shallow and deep marine env tied into the geoligic features offshoar.
continental shelf- shallow marine env
abyssel plian-deep marine env
Shallow marine biome
Coral reef- structures created by living orginisms. composed of calcite/aragonite (CaCO3). Corals are found in both temprate and tropical waters. Shallow water reefs are fromed in zone 30N to 30S of equator.Coral reefs cover 109,769 mile square
Deep marine biome
composes 75% of marine realm. average depth of sea is 2 miles. charachterized by low temp increased pressure and no direct sun light.
orginisms have adapted to harsh env.
Bioluminescence enzime that glows
2000 new spices per yr
Weathering and the formation of soils
formed by the interaction of the 4 spheres on earth
Biosphere (living orginisms)
Weathering VS Erosion
Weathering refers to any surfacil process that helps in the disingration of rocks.
Mechanical weathering phyisical process that breaks down rocks
Chemical weathering chemical process that break down rock
Erosion physical removial of rock particals by geologic agents ex running water wind glaciers and gravity
Mechanical weathering produces more surface area by breaking rock into smaller pieces.This increases the rate of chemical weathering
types of mechanical weathering
salt crystal growth
Frost wedging occures when water infultrates into cracks and fractures, freezes and expands to push the rock appart.
Occures in areas where they have repeated cycles of freezing anf thawing
Exfoliation EX gurdel
Produced when deeply burried rocks are brought to the surface through tectonic uplift or erosional process. decressed pressure causes the rock to expand and crack along sheet joints parallel to the erosional surface
Salt crystal growth(haloclasty) causes disinagration of rocks when sailine seeps into cracks and joints in rock. Water everoperates leaving behind salt crystals. salt expands as they heat up exerting pressure on surounding rock. leaves honeycomb pattern on rock
Chemical weathering must have water
Solition- dissolution of minerals by the pressance of natural week acids. rainfall typically combines w carbon dioxide in the soil to produce carbonic acid-can desolve carbonate rock
Hydrolysis involves the reaction of water w mineral components to form clay minerald
Oxidation and reduction complementary process occures together. oxidation loss of electrons
reduction gain of electrons
best example of oxidation and reduction is the formation of rust on metal objects exposes to water an oxygen
Chemical weathering factors stability of presant minerals. grain size (or surface avaibile) increase in surface area will expose more area and increase chemical weathering.
Soil horizons controled by climate
A-zone of leaching, mineral matter is strongly disolved by infiltrating water
B-zone of acculmination, minerals from A are deposited here
C-weathered bedrock materal
Fresh bedrock, soild rock
Residual siol developed in place from the decompistion of underlying bedrock
Transported soil residual soil that has been trans ported and deposited eleswhere
Laterites-soil found in tropical areas w high rainfall enriched in hydrated iron oxides Rust Red
Tundra-found in N ans S hemisphere. dark soil w thick layer of poorly decomposed vegitation with permafrost under
Pedalfers- soil in humid env w moderate precipitation midwest and eastern US
Pedocals- soil found in simi-arid or desert areas
soil erosion even thow soil are continually formes the process requires 100s of yrd. therefor we are loosing soil at a faster rate than can be created.
Soil degration, loss of soil productivity
Expansive soils, soils that shrink and swell depending on water content
Settlement, gradual compaction of soil particals
Mitigation of soil erosion (lessen)
Terracing-creating flat areas on sloping grounds
Strip croping-plant close growing crops and alternate w widely growing crops
Crop rotation- yearly alteration of soil depleeting crops w soil enriching ones
Conservation tilling-minimizes plowing wich increases soil erosion