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Title: Ecology and Evolution
Description: Notes on populations, the greenhouse effect, natural selection, and evolution. Also includes important definitions in ecology. Suitable for Higher, A-level, and IB students.
Description: Notes on populations, the greenhouse effect, natural selection, and evolution. Also includes important definitions in ecology. Suitable for Higher, A-level, and IB students.
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Ecology and Evolution
It has been estimated that there are as many as ten million different species on
earth and understanding where and how they live and interact is a branch of
biology known as ecology
...
One
result of these changes is the evolution of new varieties and species
...
In any ecosystem there is a hierarchy of feeding relationships that influences our
nutrients and energy passed through it
...
Plants are called autotrophs; autotrophs are producers (self feeding) because
they produce organic compounds by photosynthesis
...
When an organism dies, its remains provide nutrients for other types of
organisms called detritivores and saprotrophs
...
Saprotrophs are therefore responsible for the decomposition of
organic matter and are often referred to as decomposers
...
Every ecosystem has a structure that divides organisms into trophic levels on the
basis of their food sources
...
Green plants are producers and are at the lowest trophic level
...
The first consumers are primary consumers, which are
always herbivores
...
Producer -‐> Primary Consumer -‐> Secondary Consumer -‐> Tertiary Consumer
Species -‐ a group of organisms that can interbreed and can produce fertile
offspring
...
Population -‐ a group of organism of the same species who live in the same area at
the same time
...
Ecosystem -‐ a community and its abiotic environment
...
Trophic level -‐ the position of an organism in the food chain
...
For example, the following food
chain describes one set of feeding relationships
...
This food chain can be in linked with many
others
...
Arrows in a food chain show the direction of flow of both the energy and
nutrients that keep organisms alive
...
These studies reveal that at each step in the food chain,
energy is lost from the chain in various ways
...
In all three cases that lost energy cannot be passed to
the next trophic level
...
The width of each of the
layers of the pyramid is proportional to the amount of energy it represents
...
Every link in the food chain
results in loses so that eventually there will be insufficient energy to support any
further trophic levels
...
All the organic matter from an organism, including everything from living or
dead material as waste is eventually consumed by other organisms
...
Nutrients on the other hand are continually recycled
...
The amino acid may be passed onto an animal when the plant material is
eaten and then passed out of the animal’s body during excretion
...
The Greenhouse Effect
The carbon cycle
Carbon is one of the most important elements that are recycled in an ecosystem
...
Some of this carbon is returned back to the
atmosphere as plants respire
...
In some conditions plants and animals do not decay when they die and become
compressed and fossilised in a process that takes millions of years and forms
fossil fuels e
...
coal, oil and natural gas reserves have been formed and the
carbon trap in these fuels cannot return to the atmosphere unless the fuels are
burned
...
Carbon dioxide acts as a greenhouse gas and traps the heat that is radiated from
the earth's surface and keeps the earth at a comfortable level for life to exist
...
Methane gas is another gas that contributes to the greenhouse effect
...
The precautionary principle suggests that if the affect of a change caused by
humans is likely to be very harmful to the environment, actions should be taken
to prevent it, even though there may not be sufficient data to probe that the
activity will cause harm
...
Population numbers can and do change all the time and are effected by many
factors in the environment
...
Nutrients are abundant and there is little collection of waste
...
These might be competition for limited resources such as
food, space, increased predation and disease or an abiotic factor such as oxygen
might be in short supply
...
Natality -‐ the birth rate
...
Emigration -‐ members leaving the
population
...
The availability of resources such as food, water, oxygen and light limits the
growth of populations
...
Levels of waste product such as CO2 and nitrogen waste products
...
The selection pressures act on individuals because of variation, some maybe
better suited to their environment than others
...
The characteristics of a species are inherited and
passed onto succeeding generations
...
Paleontology is the study of fossils and supplies modern day science with the
evidence that evolution does exist because they show a graduation of different
characteristics among animals of different ages
...
g
...
Mechanism for evolution:
Charles Darwin proposed the theory of evolution by means of natural selection
...
This remained a theory because it postulates but can
never be completely proved
...
The fundamental basis of his argument is described below
...
(2) Yet few of these survive to maturity and we rarely see population explosions
in any ecosystem
...
The Resources may be food, territory or even the opportunity to find a mate
...
This will bring about a struggle for survival
between the members of a population
...
(4) So different members of the same species are all slightly different and this
variation is due to the mechanism of sexual reproduction
...
When an egg is
fertilised, the zygote contains a unique combination of genetic material from its
two parents
...
(5) Because of the variation, some members of the population maybe better
suited to the surroundings than others
...
g
...
These individuals will outcompete with
others; they will survive better, live longer and pass on their genes to more
offspring
...
This is called natural selection and it occurs as the fittest survive to
reproduce
...
Species that are living
today have evolved to be suited to their environment
...
The antibiotic resistance exists because of the dose of the antibiotic
...
Treating a disease caused by the resistant strains of bacteria becomes very
difficult to treat because bacteria frequently contain additional genetic
information in the form of plasmids, which they can transfer or exchange with
other bacteria
...
Antibiotic resistant and so called super bugs such as MRSA are bacteria resistant
to many antibiotics
...
Title: Ecology and Evolution
Description: Notes on populations, the greenhouse effect, natural selection, and evolution. Also includes important definitions in ecology. Suitable for Higher, A-level, and IB students.
Description: Notes on populations, the greenhouse effect, natural selection, and evolution. Also includes important definitions in ecology. Suitable for Higher, A-level, and IB students.