Year 11 Biology Yearly Revision
A local Ecosystem
1. Biotic and abiotic factors
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An Ecosystem is made up of a group of interacting organisms and the non- living parts.
Photosynthesis is the process by which plants use to capture energy from sunlight and make organic
compounds.
Biotic – living - such as plants, Animals, Micro- organisms
Abiotic- non – living factors, such as moisture, salinity, composition of soil, dissolved ions, pH,
gases, temperature, wind, viscosity.
Abiotic characteristics of environments- aquatic or terrestrial
Aquatic can be freshwater or marine ( saltwater) – there is less variation in temperature ,
pressure increases greatly with depth, water is readily available, buoyancy (floating) is high so
organisms do not need to support own bodies as much.
Terrestrial environments – are found in different climates and range in different deserts,
grasslands, temperate forests and rain forests to mountain regions. There is greater variation in
temperature during the day, year. Atmospheric pressure decreases with altitude. Availability of water
varies, problem for organisms in dry environments. Buoyancy is low in the air, so organisms have to
support themselves.
Distribution of species- Is where a species is found
Abundance- how many individuals there are at a specific time in a specific area.
Factors that determine the distribution and abundance of a species – are climate, food, shelter,
resources, interaction of organisms with other organisms.
2. Methods of estimating populations
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A transect is a straight line, usually marked by a string or tape measure. The organisms that lie
along the transect are counted.
 Random quadrats are usually squares. Organisms found in the area are usually counted. Totals
from a series of quadrats are then averaged and then multiplied the number of quadrats that
would fill the entire area, to estimate total population.
 Transects and quadrats are useful for estimating stationary populations.
 Capture- recapture- A sample of organisms is caught and tagged. These organisms are then
released back into the population. After a period of time that allows the organisms to disperse,
another sample is taken. The number of previously tagged organisms is recorded and the
population size estimated using the formula:
Population no. = number of animals tagged x number of animals recaptured
Number of tagged animals recaptured
 Sampling is justified as it is rarely possible to count every organism in a population.
3. Roles of photosynthesis and respiration.
glucose + oxygen  Carbon dioxide + water
C6H12O6+ 6O2 
6 CO2
+ H2 O
-
 Uses of energy by organisms. for growth and repair
for movement
to keep organs working
for chemical reactions
for movement of substances in the organisms
to synthesise (make) compounds.
4. A predator- an organism that feeds on another organism. A Prey – an organism that is eaten by another
organism. Habitat- part of an ecosystem where an organism is usually found.
5. Allelopathy, parasitism, mutualism, and commensalisms.
Biotic relationship
Predation
Allelopathy
Parasitism
Mutualism
Commensalisms
Definition
A relationship between members of different
species.
Is the release of chemical substances by one
species to inhibit growth of another. The chemicals
are called allelo- chemicals.
Is a relationship between two species in which one
species benefits and the other species is harmed.
The one receiving the benefit is called the parasite
and the species being harmed is called the host.
A relationship between two species in which both
partners benefit. Sometimes they cannot live apart.
Is a relationship between two species in which one
benefits while the other is neither harmed or
receives any benefit. The species receiving the
benefit is called the commensal and the other
species is called the host.
Examples
Tadpoles eat algae. Long-neck tortoise eat tadpoles.
Wasps eat aphids….
A plant will produce chemicals to poison, repel, or
prevent the growth of neighbouring plants. Penicillin
mould produces a chemical that prevents the growth of
bacteria. Bracken ferns, which are found in many
forests, release allelochemicals to inhibit the growth of
seedlings of other species.
Human tapeworm, tanenia solium, is a parasite infesting
the intestinal tract of humans. The tapeworm feeds on
the food digested by the human and the human suffers
malnutrition and loss of weight.
Lichen is fungi and algae living in a mutualistic
relationship. Root nodules containing a nitrogen fixing
bacteria, Rhizobium, shows a mutualism between the
plant and the bacteria.
Epiphytes (such as some orchids) grow on branches or
trunks of trees and use the tree as a base for attachment.
Remora fish attach to sharks with a sucker. They catch
food from the shark.
6. Role of decomposers- Matter is recycled in an ecosystem. A large part of this recycling is carried out by
decomposers such as bacteria and fungi.
7. Food chains / food webs
 Food chainsA food chain is a model that shows how energy is passed, in the form of food, from one organism to
another. The arrows between the organisms show the direction of energy flow.
Producer
1st order
consumerHerbivore
2nd order
consumerCarnivore
3rd order
consumerCarnivore
 A Food Web- A food web shows all the interacting and interconnecting food relationships.
 Trophic Interactions (feeding relationships)
Producers- Plants are called producers because they make their own food, they are able to use light energy
from the Sun to produce food (sugar) from carbon dioxide and water. Plants are autotrophs.
Consumers- an organism that feed on other living things. Animals cannot make their own food so they
must eat plants and/or other animals. Animals are heterotrophs.
There are three groups of consumers.
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primary consumers (or) herbivores- Animals that eat ONLY PLANTS.
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Carnivores- Animals that eat OTHER ANIMALS
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Secondary consumers - carnivores that eat herbivores
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Tertiary consumers- carnivores that eat other carnivores
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Omnivores- a consumer that feeds on BOTH animals and plants
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Decomposers (bacteria and fungi) which feed on decaying matter.
Trophic interaction-one in which one organism eats another.
Trophic levels- a step along a feeding chain.
Biomass pyramid- Relationship between members of a food chin expressed pictorially to show the amounts of
living matter at each trophic level.
Energy pyramid-relationships between members of a food chin expressed pictorially to show the transfer of
energy at each trophic level.
8. Adaptation- as any feature of an organism that increases its chances of survival in an environment.
There are different types of adaptations- such as structural, physiological, behavioural.
 Structural adaptation- are the anatomical features of an organism that assist it to survive. E.g., a fish
has a streamlined body which enables it to move freely with reduce friction through water.
 Physiological adaptation- are metabolic features of an organism that assist it to survive. For example, a
fish produces mucus which covers its body and allows water to flow over its scales.
 Behavioural adaptation- are things that an organism does (or doesn’t do) that assist it to survive. For
e.g., a fish swims into seagrass beds to avoid detection by a nearby predator.
9. Competition for resources- Within any ecosystem, some resources are limited. Individuals must
compete with each other for these resources to enable to survive. Competition may occur for resources such as
food nesting sites, mates, water, light, shelter. For example, if there are too many birds, some will starve and die
as there is a limited supply of food. Often there is competition for species. Over a short term if one species has
an advantage over another it will limit the growth of that population. Over a long term, competition may lead to
the extinction of the disadvantaged species.
10. Impact of humans- the impact of humans on the environment is increasing as the population of humans
increases. Impact include:
 Habitat destruction
 Pollution
 Deforestation
 Introduced species
 Global warming
Patterns in nature
1. Cell theory and cell structure.
Because of the limitations of the human eye, much of the early biological research concentrated on developing tools to help us see
very small things. As imaging technology became more sophisticated, biological discoveries abounded. Below is a timeline detailing
some of those major events in biology.
The cell theory
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Cells are the smallest living units of organisms.
All living cells come from pre-existing cells.
Each organism is made up of one or more cells.
2. Evidence to support the cell theory- During the development of cell theory scientists used microscopes
to make observations of tissue from organisms. As microscopes improved it became easier to observe
the cellular structure of tissue. As more organisms have been studied this way it has been accepted that
all living things are made of cells. The cell theory was also supported when the theory of spontaneous
generation (that simple life forms can develop from non- living substances). Francesco Redi ( Italian,
1627-1697) showed that meat did not become infected with maggots unless it was visited by flies. Louis
Pasteur (French, 1822-1888) showed that microscopic organisms called microbes made food rot and
caused diseases. In the twentieth century the cell theory was supported by identification of cell
organelles and their functions. The discovery of cellular mechanisms and processes.
3. Structures in cells
Cell organelles
Organelle
Mitochondria
Chlorplast
Golgi
Endoplasmic reticulum
Plant or Animal
Plants and animals
Plants
Plants and animals
Plants and animals
Plasma membrane
Plants and animals
Nucleus
Plants and animals
Ribosomes
Plants and animals
Vacuole
Cell wall
Primarily plants
Plants
Function
Energy transducer--Big ATP producer
Energy transducer--produces sugar
Packages and modifies synthetic products
Nascent proteins are placed inside for
modification and transport
Boundary of the cell; exchange with the
environment
Site of hereditary information; control of
cell activity
Site of protein synthesis; often associated
with ER
Storage; excretion; water balance
Protection; fluid pressure; support
Substances within the cell
Cells contain organic compounds that are mainly made up of carbon, hydrogen and oxygen, e.g.,- nucleic
acids, proteins, carbohydrates, lipids (fats). And inorganic compounds- which are composed of variety
of elements e.g.,- water, sodium chloride, carbon dioxide, oxygen.
Chemicals commonly found in tissues
Chemical
Test used
Positive result
Glucose
Benedicts solution. Heat in water bath.
Or Use clinistix
A drop of iodine added to substance
Smear across brown paper
A few milliliters of biuret solution added to test
substance in test tube, heat in water bath.
Add a few drops of silver nitrate
Blue green solution turns orange.
Clinistix turn yellow to green
Turns to purple-black
Becomes translucent
Blue solution turns purple
Add a few drops of toluidine blue
Parts without lignin stain pinky purple.
Parts containing lignin stain green-blue.
Starch
Lipids
Proteins
Chloride
ions
Lignin
A white solid precipitate
4. Chemical move into and out of cells.
Cells require basic requirements from surroundings. They release waste into surrounding and at the same
time, other molecules move in and out of cell. The movement of substances into and out of cell often
depends on the difference between the concentration of substance within the cell and the surrounding
environment. The cell membrane is responsible for the movement of molecules into and out of cells.
5. Cell membrane structure- The fluid mosaic model
The cell membranes have a double layer structure and are composed of proteins and lipids. (phospholipids,
cholesterol and glycolipids). The double layer structure is mainly due to phospholipids that form a fluid
‘skin’ which can easily change in the size. Within each layer, and sometimes through both layers, are
protein molecules that are able to move with the phospholipid layer. This structure is called the fluid mosaic
model. The fluid mosaic model containing a phopholipid bilayer with embedded proteins.
6. Diffusion and Osmosis
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Diffusion – the movement of a substance from where it is more concentrated to wher it is less
concentrated. Diffusion continues until the two concentrations are equal
Osmosis- Diffusion of water through a selectively permeable membrane.
7. Surface area to volume ratio.
The ratio of the surface area to volume ratio influences the rate at which substances move into and out of
cells. As objects become larger their surface area to volume ratio decreases. For a cell the ratio between its
surface area and its volume is very important. As the cell grows bigger, its SA/V ratio decreases . if the cell
continued to grow, its SA would not be large enough to allow sufficient exchange of substances for all cell
processes to continue.
Autotrophs- are organisms that make their own food from simple compounds. They can make organic material
from water, carbon dioxide and inorganic material using energy from sunlight, e.g., plants
Heterotrophs- are organisms that cannot make their own food and rely on autotrophs or other heterotrophs for
food.
Photosynthesis
Photosynthesis is the series of reactions in which the energy of sunlight is the trapped in the chemical bonds of
the sugar, glucose.
Photosynthesis takes place in the chloroplasts of cells and the membrane structure of chloroplasts
provide such a large surface area to increase the efficiency of photosynthesis.
6CO2 + 6H2O ------> C6H12O6 + 6O2
Sunlight energy
Structures in plants for absorbing nutrients and for photosynthesis.
Plant roots- have structures such as fibrous roots, root hairs and mycorrhizae to increase the area for absorption
of water and minerals.
Plant leaves- are flat and thin to facilitate penetration of light. Cells rich in chloroplast are packed at top of leaf
to absorb solar energy more easily. Air spaces in leaves store carbon dioxide and oxygen.
Some ways plants have of conserving water
 The stomata necessary for gas exchange open and close so that water loss by transpiration is minimized
when plants have no need for CO2. This helps to maintain appropriate water balance.
Stomata are open in daytime which permits diffusion of CO2 into the leaf for photosynthesis. At the same
time water is lost through the stomata, via transpiration.
 Epidermal cells on above-ground structures are coated with a waxy cuticle layer (cutin) to prevent
water loss.
 Plant cells have vacuoles to accumulate a volume of water, and cell walls to help maintain turgor.
 Many cells and tissues need not be maintained because they're dead (saves energy).
Differences in leaves shapes include:
 The shape and size of leaf- some plants have leaves reduced to spikes to minimize water loss.
 The thickness of the cuticle- the cuticle reduces water loss.
 The size and number of photosynthesizing cells.
 Fleshiness of the leaf
 The number and location of the stomates
 The size of intercellular air spaces
 The amount of strengthening tissue
 Other special leaf structures such as waxy layers and hair.
The shape of the leaf and distributions is directly related to the environment in which the plant lives.
Digestive systems of animals
Digestion is the breaking down of complex foods by digestive enzymes into simpler substances which can
be absorbed through the wall of the small intestine into the bloodstream
Digestive
structure
Function
Chemical
systems
composition of
diet
Herbivore
Herbivores have a long alimentary canal relative to
Plant materials,
their body size. Pant materials stay longer in digestive
cellulose.
tract as their harder to digest to the cellulose cell wall.
Many herbivores have special chambers where bacteria
and protests live and make enzymes to break down
cellulose into sugars.
Carnivore
Carnivorous animals such as Tasmanian Devil has long
pointed canine teeth for tearing flesh. Their premolars
are adapted for shearing and cutting. They have a
simple, single chamber for a stomach. The small
intestine is much shorter than in omnivores and
herbivores.
Eat meat, which
is predominantly
protein and
requires less
digestion.
Nectar
feeding
animal
(honey
possum)
It has slender long incisor teeth Nectar and pollen are
scraped off the long tongue as it is retracted. A
diverticulum branches off the stomach and serves as a
storage container for nectar.
Honey possum
feeds on pollen,
nectar and
insects.
Open and Closed circulatory systems
Open circulatory system- the circulating fluids passes through blood vessels that open into interstitial spaces.
Open circulatory systems are found in many invertebrates, e.g. Crustaceans, molluscs.
Closed circulatory system- where the circulating fluid is always contained in a set of blood vessels. Closed
circulatory systems are found in vertebrates and a few invertebrates. A heart, or a series of hearts pump blood
through blood vessels.
Transport systems in multicellular organisms
Transport mechanisms and systems move dissolved nutrients and metabolic wastes in many plants and animals.
Very small organisms such as amoeba have a large surface area to volume (SA:V) ratio. The area exposed to the
environment is great enough for them to able to obtain nutrients and get rid of waste. Algae for example, have
no special structures for gas exchange. The cells in algae are in direct contact with the surrounding water in
which gases are dissolved. Large multicellular organisms have a small SA:V ratio. They cannot carry out simple
exchange of nutrients and wastes. These organisms need a series of tubes through which all materials can be
transported.
In plants and animals the transport systems have the same function.
Transport systems in plants/ animals
Animals-the blood system
Plants- the xylem and phloem
The transport system
Carries nutrients from the
Digestive system
Roots and leaves
environment via:
Carries gases from environment
Lungs and gills
Leaves and lenticels (openings for
via:
gas exchange on woody stems of
some plants)
To tissues then remove wastes such Nitrogenous waste and carbon
Oxygen and carbon dioxide
as:
dioxide
To where they can be excreted via: Kidneys, lungs/ gills
Leaves and lenticels
Comparison of the Three Transport Systems in Animals
Life on Earth
The origins of life
Life probably originated around 3.8 billion years ago
The conditions on the earth were suitable for building life
The building blocks of life were generated either by aboitic synthesis or arrived from extraterrestrial sources.
These building blocks were used to generate the protiens, nucleic acids, and organic phosphates necessary for
life.
Life, once established, would change the environment so that life could not arise again.
Setting the stage, 3.8 Billion years ago
 The earths atmosphere is rich in CO2, H2O, N2, lesser amounts of methane and ammonia
 Temperature at the earths surface drops below 100 C
 Acidic rains fall, Erosion begins
 UltraViolet light beats down
 The earth's crust is thin and hot
 Warm mineral-rich oceans form
The Building blocks of life
amino acids
nucleic acid bases, sugars, phosphoric acid, phosphoric acid.
The Miller-Urey experiment attempted to recreate the chemical conditions of the primitive Earth in the
laboratory, and synthesized some of the building blocks of life.
Technological advances have assisted in the development of our increased understanding on the origin of
life.
Technology
Contribution to origin of life
Electron microscope
Used to closely examine meteorite samples and microfossils
Radioactive dating
Enables more accurate dating of fossils
The development of deep- sea vessels
Led to discovery of deep sea vents
Invention of mass spectrometer
Quickly and accurately analysis the chemical composition of
samples.
Space travel
Given information about conditions found in other parts of
solar system that may be suitable for life
The major stages in the evolution of living things
Formation of:organic
molecules
Time
4 billion years
ago
membranes
3.5- 4 billion
years ago
Prokaryotic
heterotrophic
cells
Prokaryotic
2.5- 3.5 billion
years ago
How they occur
Simple molecules could have formed spontaneously in the conditions
present in the atmosphere. They react with each other and form more
complex compounds. These molecules accumulated in an anoxic
environment.
As complex compounds form, membrane like structures appear.
Membranes could protect and control materials that move in and out of
cells. At some point membrane bound organic molecules were able to
reproduce themselves, beginning the development of prokaryotic cell.
Early cells- similar to bacteria. They have no internal membrane-bound
organelles. Simple one celled organisms.
2.0- 2.5 billion
The development of autotrophic prokaryotes such as cyanobacteria
autotrophic cells
years ago
Eucaryotic cells
1.2-1.4 billion
years ago
Colonial
organisms
1.5 billion years
ago
Multicellular
organisms
1.0-0.5 billion
years ago
caused major changes in earth’s atmosphere. They were self feeders and
carried out photosynthesis. With the development of autotrophs oxygen
become more abundant.
The evolution of cells progressed quickly in an oxic atmosphere.
Eucaryotic developed, with their membrane bound organelles.
Eucaryote cells have different forms, they can be plant, animal or fungal
cells.
Unicellular organisms group together to form loose associations or
colonies of organisms. Individual cells can then take on different roles.
E.g blue bottle
The next stage is the development of true multicellular organisms with
cell specialization, and differentiation of cells into tissues and organs
with specific functions
Anoxic to Oxic Transition
Throughout most of the Precambrian, Earth was dominated by Cyanobacteria and bacteria. As the free oxygen
(O2) released by Cyanobacteria slowly rusted the Earth, producing incidentally the great iron-ore deposits, the
chemistry of the global environment was changed from anoxic (without free oxygen), suitable only for
anaerobic microbes, to oxic, in which aerobic (oxygen-requiring) organisms could thrive. All familiar plants
and animals, including ourselves, are aerobic, and depend upon free oxygen for metabolism. Transition from
anoxic to oxic conditions during the Precambrian made possible the evolution of complex plants and animals
about one billion years ago.
Evidence for the origin of life on Earth
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Palaentological evidence- Fossils provide evidence of the diversity and abundance of organisms
throughout Earth’s history. They reveal organisms that are now extinct and provide evidence in changes
that have occurred in species over time.
Geological evidence- comes from rocks and landforms such as banded iron formations, red beds and
uraninite. Banded iron formations are ancient rock deposits that show there were fluctuating levels of
free oxygen available at the time. Red beds are layers of sandstone stained with iron oxide that were
common in rocks formed 2.3bya. Uraninite is uranium dioxide that occurs in ancient rocks. When the
atmosphere contains free oxygen a different compound called uranium oxide forms.
The geological evidence provides information about when Earth’s atmosphere changed from
anoxic to oxic.
Cultural differences in understanding
Every group of humans have some understanding of the beginning of time and the creation of life.
Examples of cultural explanation include:
 The fundamental creationist view- Earth was made by God in 6 days. During this time the creation of
every organism, including humans was made. This conflicts with the evidence from fossils that show
there was a gradual development from simpler to more complex organisms.
 Aboriginal dreaming- which explains that the beginning spirits created the Earth and animals and
plants, and then the spirits joined with the Earth. The Dreaming also conflicts with the information that
is derived from the fossil record.
Classification
Is the grouping of organisms with similar features. The study of classification is called taxonomy.
Kingdom- (usually 5) is the major categories that all life is classified under.