Transcript ecology and evolution

Mr. Lajos Papp
The British International School, Budapest
2014/2015
No man is an island
No man is an island entire of itself; every man is a piece of
the continent, a part of the main; if a clod be washed away
by the sea, Europe is the less, as well as if a promontory
were, as well as any manner of thy friends or of thine own
were; any man's death diminishes me, because I am
involved in mankind. And therefore never send to know for
whom the bell tolls; it tolls for thee.
John Donne 1624
4.1 Species, communities and ecosystems
Species: a group of organisms that can potentially
interbreed to produce fertile offspring.
Members of a species may be reproductively isolated in
separate populations.
Species have either an autotrophic or heterotrophic
method of nutrition (a few species have both methods).
Autotrophic: make their own food, self-feeding.
Heterotrophic: obtain carbon compounds from other
organisms, feeding on others.
Patterns, trends and discrepancies
Almost all plants and algae are autotrophic. However,
there are small numbers of plants and algae that do not
fit the trend. They do not contain chloroplasts, they
grow on other plants, and therefore parasites.
Consumers: are heterotrophs that feed on living
organisms by ingestion. (basic terms of digestion)
Detritivore: are heterotrophs that obtain organic
nutrients from detritus by internal digestion.
Detritus
dead leaves and other parts of plants,
feathers, hairs and other dead parts of animals,
faeces from animals.
Typical terrestrial detritivores: earthworms, woodlice,
millipedes, vultures and hyenas.
Saprotrophs: heterotrophs that obtain organic nutrients
from dead organic matter by external digestion: fungi
and bacteria.
They secrete digestive enzymes then absorb the
products of digestion.
Community: a group of populations of different species
living together and interacting with each other.
All species are dependent on relationships with other
species for their long-term survival.
Ecosystem: a community forms by its interactions with
the abiotic (non-biological) environment.
Air, water, soil or rock.
Ecologists study both the components of ecosystems
and the interactions between them.
Ecosystems
- continuous energy supply (energy flow)
- availability of chemical elements depends on cycles
The continued survival of living organisms including
humans depends on sustainable communities.
Autotrophs: obtain inorganic nutrients from the abiotic
environment.
The supply of inorganic nutrients is maintained by
nutrient recycling.
Chemical elements can be endlessly recycled. The
details vary from element to element.
Ecosystems have the potential to be sustainable over
long periods of time. Something is sustainable if it can
continue indefinitely. (fossil fuels not)
There are three requirements for sustainability in
ecosystems:
1. nutrient availability
2. detoxification of waste products
3. energy availability
Skills
Classifying
species
as
autotrophs,
consumers,
detritivores or saprotrophs from a knowledge of their
mode of nutrition. Handout.
Skills
Setting up sealed mesocosms to try to establish
sustainability.
http://mesocosm.eu/node/16
http://www.magzinr.com/user/D_Faure/mesocosm
Skills
Testing for the association between two species using
the chi-squared test with data obtained by quadrat
sampling.
https://www.youtube.com/watch?v=WXPBoFDqNVk
http://www.countrysideinfo.co.uk/comparis.htm
Skills
Recognizing and interpreting statistical significance.
http://www.wikihow.com/Assess-StatisticalSignificance
t-test.
A test of the null hypothesis that the means of two
normally distributed populations are equal. Given two
data sets, each characterized by its mean, standard
deviation and number of data points, we can use some
kind of t test to determine whether the means are
distinct, provided that the underlying distributions can
be assumed to be normal.
Versions of the t test depending on whether the two
samples are unpaired, independent of each other (e.g.,
individuals randomly assigned into two groups,
measured after an intervention and compared with the
other group).
If the calculated value is over the threshold chosen for
statistical significance then the null hypothesis is
rejected in favour of an alternative hypothesis, which
states that the groups do differ.
The t-test assesses whether the means of two groups are
statistically different from each other. This analysis is
appropriate whenever you want to compare the means
of two groups, and especially appropriate as the analysis
for
the
post-test-only
experimental design.
two-group
randomized
4.2 Energy flow
Most ecosystems rely on a supply of energy from
sunlight.
Living
organisms
can
harvest
this
energy
by
photosynthesis. (autotrophs)
Heterotrophs do not use light energy directly, but they are
indirectly dependent on it.
Light energy is converted to chemical energy in carbon
compounds by photosynthesis.
Producers absorb sunlight using chlorophyll and other
photosynthetic pigments. This converts the light energy to
chemical energy, which is used to make carbohydrates,
lipids and all other carbon compounds in producers.
Chemical energy in carbon compounds flows through
food chains by means of feeding.
A food chain is a sequence of organisms, each of which
feeds on the previous one.
The arrows in a food chain indicate the direction of
energy flow.
Energy released from carbon compounds by respiration
is used in living organisms and converted to heat.
Living organisms need energy for cell activities.
ATP supplies energy for these activities.
All cells produce ATP by cell respiration.
Living organisms cannot convert heat to other forms of
energy.
Living
organisms
can
conversions (examples).
perform
various
energy
Heat is lost from ecosystems.
The heat may remain in the ecosystem for a while, but
ultimately is lost.
Ecologists assume that all energy released by respiration
for use in cell activities will ultimately be lost from an
ecosystem.
Energy losses between trophic levels restrict the length
of food chains and the biomass of higher trophic levels.
Energy is lost through cell respiration.
Not all material is assimilated / consumed / not digested
/ lost in feces.
Only a small amount (10-20%) of energy is passed
between trophic levels.
Skills
Quantitative representations of energy flow using
pyramids of energy.
Worksheet.
Pyramids of energy should be drawn to scale and should
be stepped, not triangular. The terms producer, first
consumer and secondary consumer and so on should be
used, rather than first trophic level, second trophic level
and so on.
The distinction between energy flow in ecosystems and
cycling of inorganic nutrients should be stressed. There
is a continuous but variable supply of energy in the form
of sunlight but that the supply of nutrients in an
ecosystem is finite and limited.
4.3 Carbon cycling
It is important to obtain reliable data on the concentration
of carbon dioxide and methane in the atmosphere. Why?
Autotrophs convert carbon dioxide into carbohydrates and
other carbon compounds. (reduces concentration)
What increases concentration?
In aquatic ecosystems carbon is present as dissolved
carbon dioxide and hydrogen carbonate ions. This
explains how carbon dioxide can reduce the pH of
water. They both are absorbed by aquatic plants and
other autotrophs that live in water.
Carbon dioxide diffuses from the atmosphere or water
into autotrophs.
Carbon dioxide is produced by respiration and diffuses
out of organisms into water or the atmosphere.
Methane (CH4) is produced from organic matter in
anaerobic conditions by methanogenic archaeans
(single-celled microorganisms, prokaryotes) and some
diffuses into the atmosphere or accumulates in the
ground.
Methane is oxidized to carbon dioxide and water in the
atmosphere.
Methane is naturally oxidized in the stratosphere. This
explains why atmospheric concentrations are not high,
despite large amounts of production of methane by both
natural processes and human activities.
Peat forms when organic matter is not fully
decomposed because of acidic and / or anaerobic
conditions in waterlogged soils.
Saprotrophs cannot decompose totally organic matters
under these conditions.
Partially
decomposed
organic
matter
from
past
geological eras was converted either into coal or gas
that accumulate in porous rocks.
Peat is compressed and heated.
Carbon dioxide is produced by the combustion of
biomass and fossilized organic matter.
Combustion is an oxidation reaction (in the presence of
oxygen).
Fossilized organic matters (coal, oil, natural gas) are
burned as fuels. Carbon cycle, photosynthesis.
Animals such as reef-building corals and mollusca have
hard parts that are composed of calcium carbonate and
can become fossilized in limestone.
These animals die, the soft part decomposes.
Hard parts can form deposits on the sea bed.
Application
Estimation of carbon fluxes due to processes in the
carbon cycle.
Carbon fluxes should be measured in gigatonnes.
Application
Analysis of data from air monitoring stations to explain
annual fluctuations.
Skill
Construct a diagram of the carbon cycle.
A pool is a reserve of the element. The carbon dioxide
in the atmosphere is an inorganic pool of carbon. The
biomass of producers in an ecosystem is an organic
pool.
A flux is the transfer of the element from one pool to
another. (e.g.: photosynthesis)
Text boxes can be used for pools and labeled arrows for
fluxes.
4.4 Climate change
Release of greenhouse gases occurs locally but has a
global impact, so international cooperation to reduce
emission is essential.
Carbon dioxide and water vapour are the most
significant greenhouse gases.
Carbon dioxide
+: cell respiration by living organisms, combustion of
fossil fuels.
-: photosynthesis and dissolving in waters.
Water vapour
+: evaporation from waters, transpiration in plants.
-: rainfall and snow.
Other gases including methane and nitrogen oxides
have less impact.
Methane: waterlogged habitats, landfill sites, melting
ice.
Nitrogen oxides: by bacteria, agriculture, vehicle
exhausts.
The impact of a gas depends on its ability to absorb long
wave radiation as well as on its concentration in the
atmosphere.
Greenhouse effect
-
short wave solar radiation (light)
-
light penetrates the atmosphere and passes
through the molecules of the atmosphere
-
absorption by the ground and conversion to long
wave infrared radiation (heat)
-
this warms the planet
-
some infrared is lost to space as heat
-
atmospheric gases particularly water vapour,
carbon dioxide, methane, CFCs and oxides of
nitrogen
-
absorb infra-red and scatter this rather than letting
it escape to space effectively trapping the heat
-
some light reflects off the atmosphere and never
enters
-
if greenhouse effect did not exist, the average
global temperature would be -170C.
The warmed Earth emits longer wavelength radiation
(heat).
Longer wave radiation is absorbed by greenhouse gases
that retain the heat in the atmosphere.
Global temperatures and climate patterns are influenced
by concentrations of greenhouse gases.
There is a correlation between rising atmospheric
concentrations of carbon dioxide since the start of the
industrial revolution 200 years ago and average global
temperatures.
Recent increases in atmospheric carbon dioxide are
largely due to increases in the combustion of fossilized
organic matter.
Combustion: coal (from late 18th century), oil and
natural gas (from 19th century).
Application
Threats to coral reefs from increasing concentrations of
dissolved carbon dioxide.
Ocean acidification will become more severe if the
carbon dioxide concentration of the atmosphere
continues to rise.
Application
The concentration of carbonate ions in seawater is low,
because they are not very soluble. Dissolved carbon
dioxide makes the carbonate concentration even lower
as a result of some interrelated chemical reactions.
Application
Correlations between global temperatures and carbon
dioxide concentrations on Earth.
Application
Evaluating claims that human activities are not causing
climate change.
Temperatures on Earth are influenced by many factors,
not just greenhouse gas concentrations.
Global warming is continuing but not equal increases
every year.
Not all sources are trustworthy.