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Ecology: study of living things and their important
Environment: surroundings
A species is a group of organisms that very closely resemble each other and are of common ancestry;
they are normally capable of interbreeding to produce fertile offspring
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Some species don’t interbreed at all, instead they reproduce asexually; in this case the offspring
are very similar in structure and don’t have much genetic variation
Some members of different species may also interbreed; generally, the offspring there will be
will infertile
Species evolve over time meaning they aren’t easy to define; change takes place over a long
time, though, so species is an appropriate term

A species is a group of reproductively isolated organisms that interbreed to produce fertile offspring;
organisms of the same species of similar structure, which can be used to define a species
Members of a species may be reproductively isolated in separate populations
Population: all the individuals of a species in a habitat at any one time; members of a population can
interbreed
Boundaries of populations are hard to define
Community: all the living things in the habitat; a sum of all populations
Ecosystem: A community and its surroundings, the environment in which they live and their interactions
with the environment; basic functional unit of ecology
Biome: a group of ecosystems that share similar climates and typical organisms
Biosphere: our entire planet, with all its organisms and physical environments
Two features of an ecosystem:
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Self-contained unit: most organisms of the ecosystem spend their entire lives there and the
nutrients are recycled
Interactive: kinds of organisms living there are decided by the environment and that physical
environment is constantly altered by the organisms

Organisms make up the biotic component; physical environment makes up the abiotic component
The habitat is the locality where an organism occurs; if the locality is very small, then it is called a
microhabitat
The essence of survival of organisms is their activity
To carry out their activities, organisms need energy which comes from respiration; the energy of ATP
has been transferred from sugar or other organic molecules which come from nutrients
Green plants make their organic nutrients from an external supply of inorganic materials in
photosynthesis; the nutrition is described as autotrophic and in ecology, green plants are called

producers
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Autotrophs vs consumers
Great majority of green plants are autotrophic; they play a key part in food chains; in contrast, animals
and most organisms use only existing nutrients that come from digestion and absorption
Animal nutrition is dependent on plant nutrition; animals are consumers, and their nutrition is described
as heterotrophic
A heterotroph is an organism that obtains organic molecules from other organisms
A consumer is an organism that ingests other organic matter that is living or recently killed
Some of the consumers, f, feed only on plants; they are primary consumers
Animals feeding exclusively on other animals are carnivores; if carnivores feed on primary consumers,
then they are secondary consumers, and if they eat secondary consumers, then they are tertiary
consumers
Detritivores and sapotrophs
Sapotrophs are organisms that feed on dead plants and animals and on the waste of other animals; they
live in/on organic matter and secrete digestive enzymes and absorb the digestion
Detritivores are organisms that ingest dead organic matter
Feeding by sapotrophs leads to the release of inorganic material into the environment, such as carbon
dioxide, water, ammonia, and ions such as nitrates and phosphates; these get absorbed and reused by
plants
The distribution of two or more species in a habitat may be entirely random or may be based on
factors such as abiotic conditions
^eg Soils rich in calcium tend to support different population from those on dry acid soils

In order to discover whether there is an association or not, there needs to be reliable data on their
distribution; this comes from random sampling; every individual has a chance of being selected and so a
representative sample is assured
Quadrats are used to study populations and communities; it is a square frame that outlines a known
area for sampling
The size of a quadrat depends on the size of the individuals of the population being analysed and they
are placed according to random numbers, after the area is divided into several squares
Presence or absence in each quadrat is recorded; the data is subjected to statistical test, then the
observed and expected values are compared in chi-square tests
Steps of how an area is sampled:
1
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3
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The map of the habitat is marked out with gridlines
Coordinates for placing the quadrats are obtained as sequences of random numbers
Within each quadrat, the species are identified; then the density or abundance is estimated
The density, frequency, or abundance measurements are quantified through measuring the
total area of the habitat; to calculate: the mean density is multiplied by the total area, which is
then divided by the area of each quadrant
...
You divide that value by the area of one chosen quadrat, this will divide the entire population and
give you the estimate of how many from that population are in that very quadrat)

Ecosystems have the potential to be sustainable of long periods of time because organisms spend
their entire lives there and nutrients are recycled endlessly
Environments can self regulate; basis of sustainability is the flow of energy through ecosystems and the
endless recycling of nutrients
However, humans can destabilize ecosystems; result of large presence all over the globe and profligate
use of space and resources, high demand of food, and materials and minerals for homes and industries
Conservations attempts to manage the environment to reduce the human effect and maintain balance;
aims are to preserve and promote habitats and wildlife, and ensure natural resources are used to
provide a sustainable yield
It is a very active process and doesn’t just involve preservation; it also involves family planning and
population control
It is possible to study how the sustainability of an environment changes when a disturbing factor is
applied
Scientists may use a natural habitat
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Pro: it will be realistic and will simulate the actual environmental conditions

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Con: there is limited or no control over the “controlled variables”

Scientists may use a mesocosm (small scale lab model)
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Pro: There is control over the variables; measurements can be more precise in terms of stability
and impact of disturbing factor
Con: unrealistic; they aren’t always relevant or applicable to natural ecosystems

Investigation of eutrophication
Water that has inorganic ions (from sewage or fertilizer run off, plant growth is luxuriant; increase in
ammonium, nitrate, and phosphate increases plant growth; when seasonal temperature rises, the
aquatic algae undergo an algal bloom  this is called eutrophication
When the bloom dies back, the organic remains of the plants are decayed, the water then becomes
deoxygenated and anaerobic decay occurs with hydrogen sulphide; a few organisms can survive this, but
most die
Cycling of Nutrients
Nutrients provide chemical elements that make up the molecules of cells and organisms; all organisms
are made of Carbon Hydrogen and Oxygen, together with mineral elements nitrogen, calcium,
phosphorous, sulphur, and potassium and other others (in increasingly small amounts)
Plants obtain essential nutrients from carbon dioxide and water, along with minerals absorbed as ions
from the soil, to form complex organic molecules they need
Animals obtain the complex organic molecules that they require through digestion and absorption along
with assimilation
Recycling of nutrients is essential, because available resources are limited
When organisms die, the bodies are broken into simpler substances (carbon dioxide, water, and
ammonia), then nutrients are released
Detritivores generally begin the breakdown and decay, but saprotrophic bacteria and fungi complete the
breakdown; elements that are released may become part of the soil solution and some may react with
chemicals of soil or rocks before being reabsorbed
Both plants and animals ultimately depend on saprotrophic microorganisms to release matter from
dead organisms for reuse

Most ecosystems rely on a supply of energy from sunlight
Initial source of energy is generally sunlight; harvested through photosynthesis
Producers carry out photosynthesis, they are: plants, eukaryotic algae (including seaweed) and
cyanobacteria
Heterotrophs are indirectly dependent on light energy; there are the consumers, detritivores, and
saprotrophs; all use carbon compounds as a source of energy in their foods
The amount of energy supplied to ecosystems varies; percentage harvested and passed on to consumers
also varies
Eg: Sahara, there is a lot of light, but barely any gets harvested due to lack of producers
California redwood forests has little light, but a lot of it gets harvested, due to availability of
producers
Light energy is converted to chemical energy in carbon compounds by photosynthesis
Pigments are used to absorb sunlight and convert it into chemical energy, which is then used to make
carbohydrates, lipids, and other carbon compounds
Producers can release this energy through cell respiration and use it for cell activities; energy released in
this way is lost as waste heat to the environment; only some of these are used though, mostly left in the
tissue

Chemical energy in carbon compounds flows through food chains by means of feeding
Food chain: sequence of organisms, each of which feeds on the previous one; usually made of 2 to 5
organisms
Producers are always the first in a food chain as they don’t obtain food from elsewhere; subsequent
follow the order of the trophic levels
No consumer feeds on the last one in the food chain; consumers obtain energy from the carbon
compounds in the organisms on which they feed; arrows in food chain indicate energy flow
Energy released by respiration is used in living organisms and converted to heat
Living organisms need energy for:
Synthesizing large molecules
Pumping molecules or ions across the membrane through active transport
Moving things around inside the cell; or cause muscle contraction in the protein fibers
All cells make ATP through cell respiration; there the compounds are oxidized and are exothermic; the
energy released is used as endothermic energy to synthesize ATP molecules
Chemical energy in compounds is not as easily available as chemical energy in ATP
Energy transformation is never 100% efficient; not all energy from oxidation of carbon compounds in
cell respiration is transferred to ATP; the remainder is converted to heat
Heat is also produced when ATP is used; muscles warm up when contracting
Energy from ATP may reside in large molecules when synthesized; but when those molecules are
digested, the energy is released
Living organisms cannot convert heat to other forms of energy
Organisms can convert (energy)
Light to chemical through photosynthesis
Chemical to kinetic through muscle contraction
Chemical to electric through nerve cells
Chemical to heat through heat generating adipose tissue
Heat cannot be converted to any other form of energy
Heat is lost from ecosystems
Heat resulting from cell respiration makes organisms warmer; heat can be useful to make cold blooded
animals active; birds and mammals increase rate of heat generation to maintain homeostasis

Heat passes from hotter to cooler bodies; so heat produced in living organisms is all eventually lost to
the abiotic environment; the heat may remain in the ecosystem for a while but eventually it will be lost
Energy losses between trophic levels restrict the length of food chains and the biomass of higher
trophic levels
Biomass- total mass of a group of organisms; consists of the cells and tissues of those organisms,
including the carbohydrates and other carbon compounds
Biomass has energy because it includes carbon compounds; ecologists can measure this energy added
per year by groups of organisms to their biomass
The results are calculated per square meter of the ecosystem, so that different trophic levels can be
compared; the same trend is always found: energy added to biomass by each successive trophic level is
less
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Most of the energy in food that is digested and absorbed, is released through respiration use in
cell activities; lost as het; only energy available to higher trophic level is the chemical energy in
carbs and other compounds that have not been used up in cell respiration
Higher trophic level consumers don’t usually consume their entire prey, thus some energy is not
consumed there
Not all parts of the fod ingested and digested and absorbed, some material is indigestible and
egested through faeces

Only a small amount of energy is available to higher trophic level; generally, it is 10% but it can vary
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339% but it is lower above parts of the Earth’s surface where
photosynthesis rates are high
In aquatic habitats, carbon dioxide is present as a dissolved gas and hydrogen carbonate ions
CO2 is soluble in water; can either remain in water as a dissolved gas or it can combine with water to
form carbonic acid; carbonic acid can dissociate and form hydrogen and hydrogen carbonate ions to
reduce the pH of water
Both dissolved CO2 and H2CO3 ions are absorbed by aquatic plants and other autotrophs that live in
water; use them to make carbohydrates and other carbon compounds
Carbon dioxide diffuses from the atmosphere or water into autotrophs
Autotrophs use CO2 in the production of carbon compounds by photosynthesis or other processes;
reduces the concentration of carbon dioxide inside autotrophs

This sets up concentration gradient between cells of the aquatic plants and the atmosphere; CO2
diffuses into the autotrophs
Land plants with leaves have a similar diffusion through their stomata in the underside of the leaves; in
aquatic plants, the entire surface of the leaves and stems is usually permeable to carbon dioxide
Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere
Carbon dioxide is a waste product of aerobic cell respiration; all non-photosynthetic cells in producers,
animal cells, and saprotrophs have carbon dioxide as a waste product
Carbon dioxide produced by respiration diffuses out of cells and passes into the atmosphere or water
that surrounds these organisms
Methane is produced from organic matter in anaerobic conditions by methanogenic archaeans and
some diffuses into the atmosphere
Methane is a waste product of anaerobic respiration
Three different groups of anaerobic prokaryotes are involved:
1
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Bacteria that use the organic acids and alcohol to produce acetate, carbon dioxide, and
hydrogen
3
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CO2 + 4H2  CH4 + 2H2O
b
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7-1
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2 or 70 (two extremes)
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There is a correlation between rising atmospheric concentrations of carbon dioxide since the star of
the industrial revolution 200 years ago and the average global temperatures
Co2 concentrations in the atmosphere were about 260-280 until the late 18th century; this is when
concentrations probably started to rise above the natural levels; much of the rise has happened since
1950
In the late 18th century, the industrial revolution was starting in some countries but the main impact was
in the 20th century; more countries were industrialized, coal oil and natural gas use increased
dramatically  increase in atmosphere carbon dioxide
Since the start of the industrial revolution, the correlation is very marked
Recent increases in atmospheric carbon dioxide are largely due to increases in the combustion of
fossilized organic matter
As industrial revolution spread, more coal was being mined and burned, causing carbon dioxide
emissions; energy from combustion of the coal provided a source of heat and power
During the 19th century, the combustion of oil and natural gas became widespread in addition to coal
From 1950s onwards, the burning of fossil fuels became rapid, and this coincides with the period of
steepest co2 rises

Threats to coral reefs from increasing concentrations of dissolved carbon dioxide
Emissions of co2 are affecting oceans; over 500 billion tonnes of carbon dioxide released by humans
have dissolved in the oceans
The pH of surface layers of the oceans has fallen from 8
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069 (Now)
This shows a 30% acidification; it will become more severe if the CO2 concentration of the atmosphere
continues to rise
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If seawater ceases to be a saturated solution of carbonate ions, existing calcium carbonate tends to
dissolve
2012, oceanographers from more than 20 countries met in Seattle and agreed to set up a global scheme
of monitoring ocean acidification
Volcanic vents have been releasing carbon dioxide and lower carbonate ion levels, in the Gulf of Naples;
there are no corals, sea urchins, or other such animals there
Sea grasses and invasive algae replace them instead;



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