biology 2016 topic 1

1. Topicone
The binomialsystem
There are millions of species on our planet. Although
species can be very different from each other, many have
similar features that allow us to put them into groups. This
is called classification.
Kingdoms
The first big division of living things in the classification
system is to put them into one of five kingdoms. These
are based on what an organism's cells are like.
The five kingdoms are:
. animals (all multicellular animals)
. plants (all green plants)
. fungi (moulds, mushrooms, yeast)
. prokaryotes (bacteria, blue-green algae)
. protoctists (Amoeba, Chlorella and Plasmodium)
Furtherdivisions
Living things can then be ranked according to:
phylum
class
order
family

2. genus
species
The binomial system of naming species uses Latin
words. Each name has two parts, the genus and the
species. For example, human beings belong to the genus
Homo, and our species is sapiens - so the scientific name
is Homo sapiens.
Erithacus rubecula, the European Robin
The binomial system is important because it allows
scientists to accurately identify individual species. For
example, the European robin is Erithacus rubecula. It is
much smaller than the American robin, Turdus migratorius,
which belongs to a different genus.
Other classificationsystems
Cladistics is another way to classify organisms. It can use
data from DNA or RNA sequences, rather than just
physical characteristics. It emphasises the evolutionary
relationships between different species.
Vertebrates

3. Vertebrates are animals with backbones. They can be
classified according to their features, and include bony
fish, amphibians, reptiles, birds and mammals.
Bony fish
Bony fish absorb oxygen through their
gills and they have wet scales. Their body
temperature varies according to their
surroundings (organisms that do this are
called poikilotherms). Bony fish
reproduce by external fertilisation and lay
eggs (they are oviparous).
Amphibians
Amphibians usually have lungs but they
can also absorb oxygen through their
moist skin. Their body temperature also
varies according to their surroundings.
Amphibians also reproduce by external
fertilisation and lay eggs.
Reptiles
Reptiles have lungs and dry scales. As
with bony fish and amphibians, their body
temperature varies according to their
surroundings. However, reptiles reproduce
by internal fertilisation and lay eggs.

4. Birds
Birds have lungs, feathers and beaks.
They can maintain their body temperature
(organisms that do this are called
homeotherms). Like reptiles, birds
reproduce by internal fertilisation and lay
eggs.
Mammals
Mammals have lungs and fur. Like birds,
they can maintain their body temperature.
Mammals reproduce by internal
fertilisation and they give birth to live
young (they are viviparous).
Invertebrates– arthropods
Invertebrates are animals without backbones. They
include annelids, nematodes, molluscs and arthropods.
Arthropods are an important phylum of invertebrates.
They have:
. a hard exoskeleton (their skeleton is on the outside
rather than on the inside)
. a segmented body (their body has different sections)
jointed legs
Other invertebrates

5. Other invertebrate groups include:
annelids
nematodes
molluscs
Unlike arthropods, these invertebrates do not have
jointed legs.
Annelids
Annelids are segmented worms with soft
bodies. Most of the worm’s body consists
of identical segments, giving it a ‘ringed’
appearance.
Nematodes
Nematodes are tiny, thin worms without
segments. Many species are free-living
but others are parasites that cause
disease. For example, hookworms can
infect humans.
Molluscs
Molluscs usually have a broad muscular foot and may also have a shell.
Examples of molluscs include snails, slugs, squids and octopuses.

6. Floweringplants
Flowering plants can be classified according to the nature of their seeds,
seedlings and leaves. The two largest groups of flowering plants are:
Monocotyledons ,eudicotyledons (also called dicotyledons)
Monocotyledons
Wheat plants are monocotyledons
The seeds of monocotyledons each contain one embryonic leaf (the
‘cotyledon’). Many monocotyledons have leaves with parallel veins and
the parts of their flowers come in threes. Examples of monocotyledons
include:
palms
orchids
grasses
Eudicotyledons
Sunflower plants are eudicotyledonsThe seeds of eudicotyledons each
contain two embryonic leaves. Eudicotyledons have leaves with
branching veins, and the parts of their flowers come in fours or fives.
Examples of eudicotyledons include: oak trees, dandelions.
Keysandidentification
Keys are used to identify different species. A key will usually ask
questions based on easily identifiable features of an organism.
Dichotomous keys use questions to which there are only two answers.
They can be presented as a table of questions, or as a branching tree of
questions.

7. Characteristicsoflivingorganisms
Living organisms have the following characteristics in common:
. Movement - they can move and change their position.
. Reproduction – they can make more of the same kind of organism as
themselves.
. Sensitivity – they can detect or sense stimuli and respond to them.
. Growth - they can permanently increase their size or dry mass by
increasing the number or size of their cells.
. Respiration – they can create chemical reactions that break down
nutrient molecules in living cells to release energy.
. Excretion – they can excrete toxic materials, waste products of
metabolism, and excess substances (note that excretion is not the
same as egestion).
. Nutrition - they can take in and absorb nutrients such as organic
substances and mineral ions. These nutrients contain the raw
materials or energy needed for growth and tissue repair.
The first letter of each of these characteristics makes up the
acronym ‘MRS GREN’. This is a good way of remembering them.
Living organisms can reproduce

8. Living organisms can also control their internal conditions, such as their
temperature or water content.
Animals
Animals are multicellular organisms – they consist of many cells that
work together. Examples of animals include mammals (such as humans)
and insects (such as houseflies and mosquitoes).
Animalcellstructure
The main parts of an animal cell are the nucleus, cell membrane and
cytoplasm.
Animal cells:
. do not have cell walls
. do not contain chloroplasts, so animals cannot carry out
photosynthesis
. may store carbohydrate as glycogen

9. Animals usually have nerves or nervous systems for coordination, and
they are able to move from place to place.
Plants
Plants are also multicellular organisms – they consist of many cells
that work together. Examples include cereals (such as maize), and peas
and beans.
Plantcellstructure
Plant cells contain the same parts as animal cells. They also have some
additional ones:
. chloroplasts
. cell wall made of cellulose
. permanent vacuole
Otherfeaturesofplants
Plant cells contain chloroplasts so plants can carry out

10. photosynthesis. They store carbohydrates as starch or sucrose.
Cellstructure
Animal cells and plant cells have certain structures in common.
Structure Function
Cytoplasm Where most of the chemical
reactions happen
Nucleus Contains genetic material
which controls the cell’s
activities
Cell
membrane
Controls the movementof
substances in and out of the
cell
Mitochond
ria
Where most energy is
released in respiration
Ribosome
s
Where protein synthesis
happens
Plant cells have additional structures.
Structure Function
Chloroplast Absorb light energy for
photosynthesis
Cell wall Strengthens the cell and
supports the plant
Permanent
vacuole
Filled with cell sap to help
keep the cell turgid
Animal cells may also have vacuoles, but these are small and
temporary.

11. Fungi
Mushrooms, toadstools and moulds (such as Mucor) are multicellular
fungi. Yeast is an example of a single-celled fungus.
Fungalcellstructure
Fungal cells have a cell wall made of chitin (remember that plant cell
walls are made of cellulose).

12. A yeast cell
Athlete’s foot, caused by a fungus
Some fungi are pathogens, for example the fungal infection which
causes athlete’s foot.
Fungalstructure

13. A multicellular fungus showing rounded spore cases and spores and
thread-like hyphae
Multicellular fungi, such as Mucor, are organised into a mycelium -
which is made from thread-like structures called hyphae.
The hyphae contain many nuclei.
Fungalnutrition
Fungi cannot carry out photosynthesis. Instead they use saprotrophic
nutrition. They secrete enzymes onto their food so that digestion
happens outside the fungal cells. They then absorb the digested organic
products.
Fungal cells may store carbohydrate as glycogen (remember that plant
cells store carbohydrate as starch).
Bacteria
Rod-shaped Escherichia coli (E.coli) bacteria,commonly found in the
intestines of animals
Bacteria are microscopic single-celled organisms. Examples of

14. bacteria include:
. Lactobacillus bulgaricus (a rod-shaped bacterium used to
make yoghurt from milk)
. Pneumococcus (a spherical bacterium that acts as the
pathogen that causes pneumonia)
Bacterialcellstructure
Bacterial cells have a cell wall made of polysaccharides and proteins.
They do not have a nucleus, but instead they have a circular
chromosome of DNA. They may also have small extra circles of DNA
called plasmids.
Otherfeaturesofbacteria
Some bacteria can carry out photosynthesis, but most bacteria feed
from other organisms (living or dead).
Some bacteria are pathogens, for example Pneumococcus (which

15. causes pneumonia).
Protoctists
Protoctists are microscopic single-celled organisms.
Some protoctists, such as Amoeba, have features like an animal cell.
Others, such as Chlorella, have chloroplasts and are more like plants.
Some protoctists are pathogens. For example, Plasmodiumis, the
pathogen that causes malaria.
Viruses
Viruses are very small particles capable of infecting every type of living
organism. They are parasitic and can only reproduce inside living cells.
For example:
. the tobacco mosaic virus – this stops chloroplasts forming
in tobacco plants and causes the tobacco leaves to become
discoloured
. the influenza virus – this causes flu
. HIV (human immunodeficiency virus) – this causes AIDS
Virusstructure
Virus particles have a variety of shapes. They do not have a cellular
structure. Instead, they have a core of genetic material surrounded by a
protein coat. Their genetic material can be DNA or RNA, but not both.

16. The structure of a hepatitis virus
Cells,tissuesandorgans
In order of increasing complexity, multicellular organisms consist of:
organelles → cells → tissues → organs → organ systems
Structure Description
Organelle Cell structure that is specialised to carry out a particular functi
Job
Cell Basic structural and functional unit of a living organism
Tissue Group of cells with similar structures, working together to perfo
shared function
Organ Structure made up of a group of tissues, working together to
perform specific functions
Organ system Group of organs with related functions, working together to pe
body functions