LU2: THE COMPLEXITY OF LIFE STF1054 BIODIVERSITY
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- LU2: THE COMPLEXITY OF LIFE STF1054 BIODIVERSITY
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- Evolution of life Complex processes cycle elements among
different reservoirs - involves biology - has geochemical
consequences
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- Evolution of life (cont.) Different communities store and cycle
material and energy differently - diversity differences - different
biogeochemical results - different storage of biomass
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- What it means to be Alive Auto conservation The main function
of every living organism is making sure that it can continue it's
existence. Auto reproduction Any living system can reproduce or
proceeds from a reproduction. Storage of information Each organism
contains genetic information. This appears stored in DNA, and is
read and translated by proteins according to a universal genetic
code, which is common to all creatures.
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- What it means to be Alive (cont.) Breathing-fermentation Every
living being must have a metabolism that will transform energy and
matter taken from the environment into energy and compounds that
can be used by the different parts of the living organism.
Stability Through the creation and control of it's own internal
environment, all creatures remain stable in front of the deviation
of the external world. Control The distinct parts of an organism
contribute to the survival of a group and, therefore, to the
conservation of it's identity. Death
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- What it means to be Alive (cont.) Capable of transforming
energy Photosynthesis and respiration For homeostasis (regulation
and balance) For growth For reproduction Life and the second law of
thermodynamics Transformation of energy leads to disorder Life
requires the maintenance of order Homeostasis, growth and
reproduction occur at the expense of increased disorder (entropy)
of the whole system
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- What it means to be Alive (cont.) Life is characterized by:
Cells Common metabolic pathways Common genetic code Living things
include Bacteria Algae Plants Animals
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- The Origin of Life Growing evidence supports the idea that the
emergence of catalytic RNA was a crucial early step. How that RNA
came into being remains unknown. Growing evidence supports the idea
that the emergence of catalytic RNA was a crucial early step. How
that RNA came into being remains unknown. Catalysts are essential
for the chemistry of life RNA acts as a genetic messenger in modern
cells The Central Dogma of Modern Biology DNA makes RNA, RNA makes
protein, proteins are the common biological source of enzymatic
catalysis
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- Structure of the biosphere Hierarchy Species reproductive group
Population members of a single species that live in a given area
Community assemblage of interacting species in a given area
Ecosystem a community of animals, plants, microbes, etc, together
with the physical environment that supports it Biome a region with
a characteristic plant community (e.g. rainforest, desert)
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- Structure of the biosphere (cont.) Interactions between
organism and environment Eg. rainforest Alteration of environments
can impact ecosystems Cut the trees?
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- Environments Many ecosystems defined by the environment
Organisms subdivide that environment Organisms that share habitats
find niches within those habitats Strategies and living habits
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- Light On land, photosynthesis proceeds just above ground level
In water, communities may be vertically stratified In the water,
photosynthesis proceeds to considerable depths, depending on Water
clarity Sun angle Sea state
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- Light (cont.) The depth of water to which light penetrates
depends on the amount and nature of dissolved and suspended
constituents Oceanic waters contain few particles and are blue
Coastal waters contain high phytoplankton populations and are green
Estuarine waters contain lots of suspended sediments and look
brown
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- Photosynthesis Depends on the amount of light up to saturation
Depends on the color of light not all photons are equivalent Most
efficient with blue and red light, least efficient with green
light
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- Temperature Ocean temperature varies with Depth Latitude
Temperature controls rate of chemical reactions Slower at low
temperature Metabolism is defined by chemical reactions
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- Trophic Relationships Energy Transfer Primary Producers are
Autotrophs harvest sunlight Heterotrophs are Consumers eat organic
matter
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- The Trophic Pyramid: A Model of Consumption
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- Food Webs Illustrate Complex Trophic Relationships
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- Exploitation efficiency Autotroph plants & microbes
Photosynthesis or chemosynthesis Produce organic matter from
inorganic C sources Heterotroph accelerate chem reactions to gain
energy Herbivores - ~ 20% Carnivores - ~ 0.2% (not very efficient
at converting food to biomass!)
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- Biodiversity Number of species in a community Diversity indices
Simpson diversity = 1 [(proportion of species A) 2 + (proportion of
species B) 2 + ..]
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- Biodiversity over time Natural changes in diversity due to
evolution and extinction of species General increase in diversity
over time Interupted by extinction events Extinction is natural
Over 90% of species that have evolved are extinct
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- Recent changes in biodiversity Present day extinction is across
the board affects many groups Other extinction events affected
species within particular groups other groups survived Example is
K-T extinction of dinosaurs; mammals and plants survived to
reradiate Modern extinction associated with spread of human
populations Over hunting/fishing Habitat destruction deforestation
& coral bleaching
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- Deforestation and soil nutrients Distinct differences in
storage of biomass & nutrient cycling between temperate &
tropical forests Temperate forests have thick, rich topsoils Humus
layer of organic materials on top of subsoil Nutrients stored in
soils Tropical soils are highly weathered (lots of rain) Lateritic
clays depleted in nutrients Thin humus layer Nutrients stored in
biomass
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- Deforestation and recovery Rainforests loss of rainforest trees
leads to loss of nutrients & changes in the water cycle
Temperate forests recover because nutrients retained in the
soils
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- Deforestation & water cycle & climate Elimination of
tropical rainforests disrupts regional water cycle Minimizes
evapotranspiration (source of H2O to atm) Decreases soil moisture
and increases runoff Increases erosion rates General circulation
models to predict Net temperature increase Decrease in soil
moisture
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- The water cycle
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- Biodiversity and deforestation in tropical areas Half of the
living species are found in rainforests Forest plants have medical
value Treatment of diseases Forest plants have agricultural value
Need genetic diversity for long-term health Need variety to limit
vulnerability to diseases and pests Modern agricultural practices
limit diversities Centers of genetic diversity for crops come from
areas threatened by development, population pressures,
deforestation Seed banks
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- Biodiversity and ecosystem stability Relationship is complex In
some settings environmental stability leads to high diversity In
others, high diversity is thought to result from disturbances of
intermediate frequency and intensity How does loss of biodiversity
impact ecosystem? Remove enough species and ecosystem collapses
System maintained by a few keystone species
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- Causes of deforestation Social, political, and economic drivers
Economic arguments people and countries need hard currency (Nepal)
Motivation not to Who will bear the costs of not exploiting
resources? Earth will recover, will humans survive?
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- The Elements of Life In addition to energy, life requires
certain material substances All organisms require 23 basic elements
Availability of these elements can limit growth and survival
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- The Carbon Cycle A basic building block of life Largest of all
biogeochemical cycles Availability rarely limits marine
productivity
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- The Nitrogen Cycle N is a critical component of proteins,
nucleic acids and pigments (e.g. chlorophyll) Traditionally viewed
as the most limiting nutrient in the sea Liebigs Law of the Minimum
Growth is limited NOT BY THE TOTAL RESOURCES AVAILABLE but by the
single resource in shortest supply,
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- The Nitrogen Cycle Free N 2 comprises 80% of the atmosphere Not
generally biologically available Biological availability requires
FIXATION Most of the anthropogenically fixed N ultimately winds up
in our rivers, estuaries & coastal waters where it promotes
HARMFUL ALGAL BLOOMS
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