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185 Cards in this Set

  • Front
  • Back
If one species differs from another it is called....
Interspecific variation
If members of the same species differ from each other it is called....
Intraspecific variation
What can scientists not measure when figuring out variation? What do they do instead?
Every individual of the species, they take samples
What does a sample need to be if it is relied upon?
Representative of whole population
Name two ways a sample may not be representative...

Sampling Bias = purposeful choices

Chance = unavoidable

How can you avoid bias when making a sample? What is the method?
Random sampling = Divide area into grid of numbered lines, use random numbers generated by a calculator, take samples at the coordinate intersections
How can you minimise the effect of chance?

Use a large sample size = more reliable results

Analysis the data = has chance affected it?

What two factors influence variation?

Genetic and environmental factors

What 3 ways can genetic differences cause variation?

1. Mutations = sudden changes as chromosomes are passed on

2. Meiosis = nuclear division, mixing up genetic material

3. Fusion of gametes = sexual reproduction, fusion is random

Which way can asexually reproducing organisms be varied?

Give three examples of environmental influences, how many genes control them?
Climatic conditions, pH, soil conditions - many genes control them
Name three genetic factors that can cause variation, how many genes control them?
Blood type, eye colour, skin colour - only one gene controls them
What is it called when a characteristic is controlled by many genes?
What is the mean?
Measurement of the average, does not show range
What is the standard deviation?
measure of the spread around the mean
What makes the DNA different in organisms?
the proteins and amino acid sequence
What is different between organisms?
The alleles
The greater the number of different alleles that the members of a species possess....
The greater the genetic diversity
What does a greater genetic diversity mean for the species if the environment changes?
They are more likely to be able to cope, they are more likely to have the characteristics that suits the new environment
What is selective breeding?
Identifying individuals with desired characteristics and using them to parent the next generation.
What happens to the alleles in a population that have be selectively breed?

It is restricted to a small number of desired alleles and therefore reduces genetic diversity

Give an example of selective breeding
To produce high-yielding crops
What is the founder effect?

When a few individuals colonise a new region. They hold a small fraction of alleles so there is less genetic diversity, less able to adapt to changing conditions
What are genetic bottlenecks?

When a population suffers a dramatic drop in numbers with only a few survivors. They have a small variety of alleles and genetic diversity is low. As they bred, genetic diversity remains restricted

Name two For arguments for selective breeding

New breeds can be fashionable and desirable

More crops can improve famine cases

Name three Against arguments for selective breeding
Interfering with nature, reduces genetic diversity, new breeds can be in pain
What does DNA determine?
The inherited characteristics and the genetic codes
Describe the structure of DNA

Double helix = made up of nucleotides ( 3 parts )

De-Oxyribose, phosphate group, organic base

Name the four organic bases

Single bases = Cytosine and Thymine

Double bases = Adenine and Guanine

How are the organic bases combined and to which complementary bases?
bonded by condensation reactions, AT, CG

What does the bonding between the sugar and the phosphate group result in?


What is the name given to long chains of nucleotides?

How are the phosphate group and the Oxyribose molecules arranged?
They are alternated
What do the bases contain?
How many hydrogen bonds form between A and T

How many hydrogen bonds form between G and C


What is meant by the double helix?

Two polynucleotide chains twisted

What is the function of DNA?

Responsible for passing genetic material from cell to cell. The variety of sequences of bases on a DNA molecule provides variety
How is the DNA molecule adapted to carry out its function?

Stable = can be passed on

Two strands connected by hydrogen bonds = allows separation from DNA replication

Large molecule = carries a lot of information

Base pairs in middle = genetic information protected

What is a gene?

Sections of DNA that contains information for making polypeptides, that eventually combine to make proteins

How does DNA code for amino acids?

Through the triplet code
What are the sections that do not code for amino acids called? What are the ones that do?

Introns, Extrons
Name three features of the triplet code

It is universal, the start and end of the sequence are the same, the code in not overlapping
What are the DNA like in prokaryotic cells?

Small, circular, not associated with proteins, do not have chromosomes

What are the DNA like in eukaryotic cells?

Larger than prokaryotic, linear, associated with proteins, are chromosomes
When are chromosomes visible?

When the cell is dividing

What is the single point called in a chromosome?

What is one thread of a chromosome called?


How are the DNA in chromosomes held in position?

By proteins
A double helix is ( 2 describing words )

Coiled and folded

How many chromosomes does a human cell have?

Why is there normally a even number of chromosomes?
Chromosomes are arranged in homologous pairs
What is a diploid number?
The full number of chromosomes in a human cell

What is the haploid number?

The number of chromosomes in a gametes, 23 in a human gamete

What is a allele?

A version of a gene

What are the two ways in which cells can divide?

Mitosis and Meiosis
Describe the process of meiosis

1. Homologous chromosomes pair up

2. Chromatids wrap round each other

3. Crossing over - alleles shared

4. One set of chromosomes goes into 2 daughter cells

5. Chromatids move apart, four cells formed with a haploid number of chromosomes

What is the locus?

The position of a gene on a chromosome
Meiosis causes genetic variation by...

Independent segregation = chromosomes line up alongside homologous pairs, arrange themselves randomly

Describe crossing over...

Chromatids become twisted, bits break off, re-join to the other chromatid, new combinations produced
What are the two main stages of cell division?

Nuclear division - nucleus divides

Cell division - when the cell divides

What must happen before nuclear division?

DNA must be replicated

Describe the process of the Semi Conservative replication model

1. Enzyme Helicase breaks hydrogen bonds

2. Double helix separates

3. Exposed polynucleotide is attached by complementary nucleotides, energy is needed

4. Polymerase joins together the new nucleotides

5. Each DNA molecule contains old and new strands

When is scientific progress made?

When new evidence is produced
What is produced through mitosis?

Two daughter nuclei that have the same number of chromosomes than the parent cells

When is mitosis important?

For repair, growth and specialisation
Describe Interphase

-getting ready to go into mitosis

G1 = proteins synthesised

S = DNA replicated

G2 = organelles grow and divide, energy stores increase

Describe Prophase
Nucleus condenses, becomes visible and envelope disappears
Describe Metaphase

Chromosomes arrange in the middle by fibres
Describe Anaphase
Chromosomes migrate to opposite poles

Describe Telophase

Chromosomes can not be seen as nuclear envelope reforms

Describe Cytokinesis

Centre of cell contracts, pinching the cell into two, one nucleus each

Describe Cancer

- Group of diseases caused by uncontrollable growth of cell

- Treatment includes blocking a part of the cell cycle

What is species diversity?

The number and variety of living organisms in a particular area
What does species diversity consist of?
The number of different species and the number of individuals of each species within one community
What is genetic diversity?

Variety of genes possessed by the individuals of one species

What is ecosystem diversity?

range of different habitats within an area
The greater the diversity index...

The more stable an ecosystem usually is and the less it is affected by climate change

What is the species diversity in extreme conditions?

Low as less species have the correct adaptations to survive

How does agriculture affect species diversity?
As farmers select species for particular qualities to make them more productive. The genetic variety is reduced as the alleles are selected. Species diversity is low
Why carry out species diversity index?

Tells how many individuals and species, some may be present in low numbers

Small organisms have a....

Large surface area to volume ratio

Large organisms have a....

Small surface area to volume ratio

Specialised exchange surfaces have...

- a large surface area to increase exchange

- Thin surface for short diffusion pathway

- Partially permeable to select materials

- Movement of environmental medium

- Movement of internal medium to maintain diffusion gradient

What is the Fick's law equation?

Surface area x Different in concentration

Length of diffusion path

Describe gas exchange in single-celled organisms

-Large surface area to volume ratio

- No diffusion barrier to gases

- Can just diffuse over surface

Describe gas exchange in insects

-Spiracles on body surface open and close to allow water to evaporate

-Tracheae, network of tubes

-Tracheoles, extend throughout all body tissues

-The muscles can create mass movements of air in and out of the tracheae

Describe gas exchange in fish

-Gills, made of gill filaments stacked in a pile

-Gill lamellae increases surface area

-Counter current = blood and water flows in opposite direction maintains diffusion gradient all the way

Describe gas exchange in a leaf

-Stomata = pores on underside of leaves, surround by guard cells, controls rate of gaseous exchange

What determines what system a organism has?

The surface area to volume ratio and how active the organism is

Describe the heart transport system

-Closed system

-Blood is returned to boost its pressure


-Diffusion at end of journey

What do blood vessels do?

To allow rapid transport of blood and to control its flow

Describe the Arteries

-Carry blood away from heart

-Thick muscle layer, can control blood

-Thick elastic layer, to keep pressure high

-Thick wall, prevent bursting

-No valves, constant high pressure so no need

Describe the Capillaries

Exchanges materials into cells

-Thin wall, short diffusion pathway

-Highly branched, large SA

-Lumen narrow, red blood cells squeezed reduces pathway

-Tissue fluid, to reach every cell

Describe the Arteriole

Carry blood under low pressure between arteries to capillaries

-thick muscle wall, constriction and blood flow controlled

-Elastic layer thin, blood at lower pressure

Describe the Veins

Transport blood from tissues to heart

-Muscle layer thin, doesn't need to constrict

-Elastic layer thin, low pressure

-Valves, ensure blood doesn't flow backwards

Describe the path of blood through vessels
Arteries, arterioles, capillaries, veins
What is the tissue fluid?

-Contains glucose

-Supplies substances to tissues

-Receives CO2

-Formed from blood plasma

-Water potential controls movement

-Excess fluid returns via the lymphatic system

What is hydrostatic pressure?

Vessels get narrower creating pressure forcing tissue fluid out of the blood plasma. When released there is a lower water potential in vessel so the fluid moves back in
If a species was closely related, the DNA base sequences area....
more similar than more distantly related species
What is DNA hybridisation?

-DNA from two species is heated so double helix separates

-One species is labelled with radioactive material and mixed with other DNA

-It is cooled to allow the DNA to recombine

-The more complementary bases, the more energy needed to separate and the more closely related the species area

Describe Immunological comparisons

Serum from species A injected into species B, antibodies produced. Serum extracted and given Species C, response forms a precipitate. The greater the number of similar antigens, the more precipitates and the more closely related the species are.
What is courtship behaviour?
Helps achieve: Recognising members of own species, identifying a mate of capability to reproduce, form a pair bond, synchronise mating
What is a stimulus response chain?

When a male carries out an action and the female responds positively or negatively
Single celled organisms perform....

all function inside the boundaries of a single cell which is not very efficient
All cells are initially....

Identical but as it matures they become specialised to suit a function

Every cell contains the genes needed to.....

develop into any one of the different cell types

Once a cell is specialised....

it loses its ability to carry out other functions but specialisation is effective

What are tissues?

Tissues are cells grouped together with the same function

Example of a tissue...

Epithelial tissue, line surfaces of organs as protective function
What are organs?
Combination of tissues that are coordinated to perform a variety of functions

Example of an organ..

Stomach, carries out digestion, muscle to churn, epithelium to protect, connective tissue to connect

What is an organ system?

Organs working together to form a system
Describe the structure of haemoglobin

Primary= four polypeptide chains

Secondary= Chains coiled into helix

Tertiary= Folded into a precise shape

Quaternary= each chain connected to a haem group containing iron

What is the role of haemoglobin?

Transport oxygen, needs to readily associate with oxygen and dissociate with it at tissues requiring it
How does haemoglobin bind/release oxygen?
It changes shape in the presence of carbon dioxide so that it binds more loosely to oxygen and releases it
Haemoglobin with a high affinity of oxygen....

Take up oxygen molecules more easily
Haemoglobin with a low affinity of oxygen...

takes up oxygen less easily and releases it easily

An organism living in an environment with little oxygen...

requires haemoglobin with a high affinity of oxygen. The metabolic rate will not be as high as it doesn't need to release oxygen as quickly

An organism with a high metabolic rate...

needs to release oxygen readily into the tissues so need haemoglobin with a low affinity of oxygen

What does haemoglobin have different affinities?

Because they have slightly different sequences of amino acids
The process by which haemoglobin combines with oxygen is called...

The process in which haemoglobin releases oxygen is called...

At very low partial pressures of oxygen...

the four polypeptide are closely united so it is difficult to absorb the first oxygen molecule
The further the left the curve...

The greater affinity the haemoglobin has for oxygen

At the lung the level of CO2 is....

low because it is being diffused out, haemoglobin has a high affinity for oxygen as there is a high concentration of it

At respiring tissues the level of CO2 is....

high. The affinity of haemoglobin for oxygen is reduced and the curve shifts to the right

A pH is lowered when carbon dioxide levels are lowered...

haemoglobin changes shape and the oxygen is unloaded more readily.

Describe starch


-Energy source

-Alpha glucose



Describe glycogen


-Short chains

-Highly branched

-Carbohydrate storage

-alpha glucose

Describe cellulose

-Beta glucose

-Straight, unbranched

-Cross-links, micro fibrils groups to form fibres

Describe the lead palisade cell

-Carry out photosynthesis

-Continuous layer to absorb sunlight


-Vacuole pushing chloroplasts to side

Describe chloroplasts

-Double plasma membrane

-Grana, stacks of discs containing chlorophyll

-Stroma- Fluid filled matrix

How are chloroplasts adapted?

Large surface area, stroma possesses enzymes to carry out photosynthesis, contain DNA and ribosomes so can make proteins for photosynthesis

Describe the cell wall

Cellulose, middle lamella = thin layer marking boundaries, provide mechanical support, allow water to pass through

What is the casparian strip?

Waxy waterproof substance in endodermis
What are root hairs responsible for?

absorption of water and minerals

How do plants lose water?

Root hair cells provide...

a large surface area and a thin surface layer so materials can move easily
In damp conditions...

root hair cells are surrounded by soil solution with small quantities of minerals so has a high water potential. The root hair cells have a much lower water potential, water moves by osmosis down the water potential gradient.
What are the two ways what can be absorbed across the root?

Apoplastic and symplastic
Describe Apoplastic
Water pulls more water along behind it by cohesion tension, drawing water along the cell wall in the cortex. The cellulose cell walls have many water filled spaces meaning there is little resistance to pulling water

Describe Symplastic

Takes place across the cytoplasm as a result of osmosis. The water moves through the cell wall by plasmodesmata filled with cytoplasm. Water enters by osmosis increasing water potential, root hair cell has a higher water potential than first cortex cell, water moves down gradient

What prevents the apoplastic pathway?

the casparian strip in the cell wall, symplastic pathway then takes over
Passage of water into the xylem...

Active transport of salt, requiring energy in carrier proteins through the cytoplasm. Minerals in the xylem now creates a lower water potential and water moves in by osmosis which creates root pressure

Evidence of root pressure...

pressure increases with a rise in temperature

Metabolic inhibitors prevent most energy and ceases root pressure

a decrease in oxygen causes a reduction in root pressure

Movement of water up stems...

main force is evaporation known as transpiration which is when water molecules evaporate through stomata
Movement of water out through stomata...

The humidity of the atmosphere is less than air spaces in stomata, water vapour molecules diffuse out into the atomosphere
Movement of water across the cells of a leaf
Mesophyll cells lose water to the air spaces, these cells then have a lower water potential and water enters by osmosis from other cells etc etc
What is cohesion tension?

movement of water up the stem in the xylem

Water evaporates from leaves, water molecules form hydrogen bonds between each other and stick together, unbroken pathway. As water evaporates more molecules are drawn up -- transpiration pull

Evidence of cohesion tension

change in diameter of tree trunk - day = transpiration high so trunk shrinks

when xylem is broken and air enter water is not long drown up as it can not bond

water does not leak out if the xylem is broken as air is drawn in

Transpiration pull is passive meaning...

it does require energy

what effects transpiration?

Light - more light= more photosynthesis = more stomata open

Temperature = increase kinetic energy, increases movement of water, more evaporates

Humidity = more water vapour in air, less water potential gradient, less transpiration

air movement = humid layer, water potential gradient

How do you measure water uptake?

By using a potometer

Describe how you would use a potometer

1. Leafy shoot cut under water

2.Potometer filled with water with no air bubbles

3.Ruber tube, leafy shoot fitted under water

4.All joints sealed with waterproof jelly

5.Air bubble introduced

6.Distance air bubble has moved =volume of water lost

7.Reservoir tube to move air bubble

What is a xerophytic plant?

A plant that does not have a plentiful water supply and therefore has to adapt to the lack of water

How does a thick cuticle prevent water loss?

Less water can escape
How does a rolled up leave prevent water loss?

Creates still air within rolled leaf so there is no water potential gradient for water to diffuse out of the stomata
How does hairy leaves prevent water loss?
It traps moist air next to the leaf, the water potential gradient is reduced and less water is lost by transpiration

How does a reduced surface area to volume ratio reduce water loss?

The slower the rate of diffusion
What is adaptation?

The process of natural selection which organisms adjust to suit their environment changes

What does adaptation increase?

Long-term reproductive success

How are bacteria killed?

Through antibiotics

How do organisms gain diversity?

Changing quantity or structure of DNA through a mutation. Recombine the existing DNA during sexual reproduction.
How does bacteria gain diversity?

Mutations and conjugation
Describe mutations

result in different characteristics

one or more bases added, deleted, replaced

changes in amino acid sequence

leads to a different polypeptide and different protein

Describe conjugation

Occurs when a bacterial cell transfers DNA to another bacterial cell

How does conjugation work?

One cell produces thin projection called conjugation tube

Donor cell replicates one of its small plasma DNA

It is broken to become linear and pass along the DNA

What is horizontal gene transmission?

Conjugation, DNA in the form of genes passed from one species to another species
What is vertical gene transmission?

Where genes are passed down from one generation of a species to the next generation of the same species

What are antibiotics?

substances produced by living organisms that can destroy or inhibit growth of microorganisms

How do antibiotics work?

They prevent bacteria from making cell walls. They inhibit the synthesis of peptide cross linkages in the wall. The walls weaken and can not withstand the pressure. Osmotic lysis occurs when water moves in by osmosis
How does bacteria become resistant?

Through mutations
What is classification?

the organisation of living organisms into groups
Define species
organisms similar to one another but different from members of other species, similar genes, closely resemble each other. They are capable of breeding to produce live and fertile offspring
How are species named?

The binomial system

Explain the binomial system

Universal system

Latin, italics

First name is generic name, denotes genus, capital letter, shared by close relatives

Second name lower case, specific name, denotes species, not shared by other species

What do you put if you don't know the specific name of a organism?


Classification of species is...

regularly changing due to increasing knowledge of evolution, physical features, biochemistry, behaviour increases

What does classification allow?

allows better communication, avoids confusion

What are the two main forms of biological classification?

Artificial classification - analogous characteristics, appearance

Natural classification - base upon evolutionary relationships, shared features between ancestors, no overlap

What is the order of classification?

Kingdom, Phylum, Class, Order, Family, Genus, Species
What is a taxon?

Each group within a natural biological classification e.g. Kingdom

What is taxonomy?

The study of positions in a hierarchical order known as taxonomic ranks

What is phlogeny?
the evolutionary relationship between organisms