Ch 8: Biosphere Flashcards
Zone of life:
relatively thin, life-supporting layer. Between the upper troposphere and the uppermost portion of the lithosphere.
Biosphere:
is an open system, series of ecosystems nestled within each other. Biomes –> ecosystems and communities and populations and individual.
All true living things share:
metabolism, growth, reproduction, evolution
Metabolism:
Energy sources: light, chemical reactions.
Used to maintain processes within the organism.
Energy is released as: heat and poop.
Chemical reaction energy sources:
chemosynthesis, biochemical (consumption)
Growth:
organization of small molecules to make large chain or sheet-like molecules. Energy is absorbed.
Reproduction:
most living material is organized in self-contained individuals.
Reproduction types:
asexual: separating off part of an individual
sexual: sharing of material from two individuals
Evolution:
fossils preserved in sedimentary rocks indicate that living things have changed over time
Cells:
most large organisms are divided into cells.
Unicellular organisms: prokaryotes
single celled, no distinct nucleus or organelles. Includes: bacteria, cyanobacteria.
Eukaryotes
generally multicellular. Contain a true nucleus. Complex internal structure: outer membrane, cytoplasm, organelles.
Cell Division allows:
unicellular organisms to reproduce, multicellular organisms to grow
Biological Polymers:
Protein, nucleic acid
DNA:
deoxyribonucleic acid. Sequence of bases contains code for constructing proteins. Carries genetic information, self replicating molecule: each strand in the double helix acts as a template for a new molecule.
RNA:
ribonucleic acid. Similar structure to DNA, forms on DNA template, carries information from DNA to sites of protein formation (ribosomes) builds proteins in ribosomes.
Evidence of biospheric change: fossils
May consist of original material, chemically altered skeletons, casts and moulds, traces.
Interpreting the fossil record:
Fossil group family trees. Natural selection as a plausible mechanism of evolution.
Technology: evolutionary history
changes to DNA occur at a roughly constant rate. Molecular clocks.
Molecular Clocks:
compare DNA, RNA or protein from two related species to estimate how long ago they separated.
History of life: chemical evolution
earliest stages in evolution must have involved polymers combining without surrounding cell membranes
First prokaryote cells recorded around
3.5Ga, Apex Chert, WAustralia.
Rise of oxygen: photosynthesis
stromatolities in limestone built by photosynthetic cyanobacteria
Rise of oxygen: BIF
Increase of oxygen in atmosphere allowed deposition of extensive iron-oxide sediments on continental shelves.
Eykarotes
eukaryotes possibly originated from combinations of prokaryotes
Ediacaran fauna
organized multicellular organisms with no known descendents
Cambrian explosion
rapid appearance of diverse multicellular animals. (related to phyla), Evolution of a gut then shells
Rapid diversification:
continued in marine environments, moved onto land as food became available.
Human evolution: Homo Sapiens
largest impact on the Earth’s surface of any species since the Cambrian explosion.
Major extinction events:
Phanerozoic era, usually followed by rapid appearance of new groups
Taxonomic classification:
Kingdom - Phyla - Class - Order - Family - Genera - Species
Species concept
variability of living things is discontinuous. Divide organisms into discrete species. Individuals have many characteristics in common.
Interspecies variation:
differences between species
Intraspecies variation:
differences within a species
All species show variation due to:
genetics and environmental influences
Genetics: inheritance and mutation
genetic variations tend to be passed on to the next generation. Variations are a result of mutations.
Genetics: Artificial selection
variation exploitation by farmers and breeders
Environmental: Competition
almost all species in the wild produce more offspring than survive to adulthood.
Competition for resources, habitat and predation.
Genetics:
inheritance and mutation
Environmental
competition, natural selection, habitat changes, population isolation, migration
Environmental: natural selection
offspring that live long enough to reproduce are best suited to their environment. Environment selects variations that favor survival.
Environmental: habitat changes
variations best adapted to the new environment (preferential survival). Species evolve with the new characteristic.
Environmental: population isolation, migration
Geographic isolation, selection pressures lead to different changes in the two populations.
Define biomes
regions where climates, habitats and ecosystems have similar characteristics.
Ecological positioning:
Niche, Habitat
Niche:
each organism has a specific role or level or position of importance
Habitat:
each organism perform and tend to occupy a specific site or location.
Provinciality:
barriers to migration. endemic species, unique ecosystems.
Biosphere energy
trophic classification based on source of energy, autotrophs, heterotrophs
Autotrophs:
photosynthesis or chemosynthesis
Heterotrophs:
energy through consumptions (biochemical)
Food chains & trophic levels
species may be arranged in trophic levels.
Feeding relationships form …
the food chain or food web.
Competition
if two organisms with the same ecological niche are present in an ecosystem they tend to compete. (Inter or intra species)
Energy flow on food chains
energy is lost at various points, respiration (excretion, heat)
Primary Production (PP)
organic carbon formed by the autotrophs in an ecosystem
Gross Primary Production (GPP)
represents energy capture by autotrophs
Typically between __% and __% of organic carbon is respired by autotrophs
25 - 75
Net Production (NPP)
NPP = GPP - Respiration
Populations: exponential growth
Unlimited resources, minor competitions, if growth rate per individual is constant, population can growth exponentially
Populations: logistic curve
eventually competition for resources slows growth, eventually birth rate = death rate. Population is at carrying capacity
Gaia hypothesis
proposed by James Lovelock and Lyn Margules.
Life has altered the environment at global scale throughout Earth history. Life tends to stabilize the environment at global scale by reducing variability of physical and chemical factors. These alterations increase probability of persistence of life.
Human interference in natural cycles…
far exceeds that of any other species on this planet.
Earth is a complex system
A single change may seem insignificant but cumulative change may be significant
H.D. Thoreau, 1840:
The impression: an apparent lack of influence of humans on oceans
Human interference: population growth
initial growth due to agriculture, technology increased the rate, but all life has a a finite limit to what can be supported
Technology is a double edge sword:
blamed for the increasing rates of changes in Earth, but necessary to understand the global connections between the Earth’s components and our influence.
Effects of a growing populations:
Landscape alteration, air/water/noise pollution, increased confrontations with the environment. Overuse of resources.
Global effects of humans: Primary
deforestation/desertification, exotic species introduction, extinctions
Global effects of humans: Secondary
spread of diseases species, decrease in genetic diversity and changes in species competition.
Human growth in the past…
often lead to mass extinctions. (New Zealand, North America, Australia) Endemic species fare poorer.
Reasons for extinctions:
loss of habitat, over-harvesting, changes in competition, lack of genetic variability.
Biodiversity loss: hotspots
25 terrestial; 10 oceanic. Reduced by `10% in size, over 70% loss of primary vegetation.
Loss of species limits
gene availability, decreasing gene pool = extinction, gene pools are replenished by wild strains.
Agriculture:
impact is increasing:
Middle East 10,000 BP
Americas: 5,000 BP
Tropical Asia: 42,000 BP
Agriculture requires:
Clearing of native vegetation, replacement.
Deforestations causes
causes significant changes in vegetation. Effect most pronounced in tropical regions. Increased settlements, agriculture and grazing. Yet soil quality is often extremely poor.
Deforestations: secondary effects
hydrological changes, soil erosion and desertification
Deforestation: hydrological changes
namely infiltration, runoff and evapotranspiration. Vegetation actually promotes rainfall
Deforestation: soil erosion
common end result of deforestation, arable land is limited; even careful use exposes the land periodically
Agriculture has a major influence on the world economy, estimated up to
7% loss in arable land each year
Desertification effects:
crop failure, decreased biomass (PP), decreased fuel supply, dune advancement, population displacement, solar radiation changes, hydrological cycle changes, overall effect: climate changes.
How many elements are required for life
24
Macro-nutrients
required in large amounts:
N,O,P,H,C and S
Micro-nutrients
required in smaller amounts:
Mn,Fe,Si,Na,Ck,B,Cu,Zn and Mo
Concentration of elements in nature
concentration in cells > environment
Law of the minimum
most limiting factor controls the response of the individual. Alleviating the control of one factor results in a new limiting factor.
Environmental gradients - thresholds
organisms have a range of tolerance, occurs along some gradient based on resources based on resources or a limiting factor.
Dose-response curve:
% of population affected versus the toxin concentration in the environment
Toxicity:
dosage at which substances have a poisonous effect, varying from a mild effect to life threatening situations.
Tolerance and toxicity
varies among species and within species (population and individual ranges)
Bioaccumulation
concentration increases through consumption
The carbon cycle
involves biological and physical processes that are closely linked.
Carbon is the key cycle
basis of life, GHG, regulates ocean acidity, key component in sediments and sedimentary rocks
Forms of carbon:
carbon dioxide, bicarbonate ions, carbonate ions.
Organic carbon: reduced
organic polymers: protein, DNA. Carbohydrates, buried organic remains, fossil fuels.
Human influences on carbon cycle:
burning fossil fuels, land use changes (deforestation, urbanization)
Our increasing rate of transfer to the atmosphere,
cumulatively increasing each year
Changing temperature and precipitation can lead to more complex environmental feedback responses such as:
vegetation changes, ice cover, sea level fluctuations, rate of decompositions, breakdown of gas hydrates.
Altering land use results in:
changing albedo, absorption, evaporation, gas exchange with the atmosphere, cloud coverage, hydrological cycle.
Our habits and economy,
changes atmospheric composition, biosphere, and hydrosphere.
