year 10 EOY exam- science

deoxyribonucleic acid

self replicating molecule present in all living organisms. Main constituent of chromosomes

chromosome

Threadlike structure of nucleic acids- carry genetic information in the form of genes

homologous

Having the same/similar structural features and patterns of genes

gene

length of dna that carries the genetic code for a particular characteristic

nitrogen base

cytosine, adenine, guanine and thymine

trait

a genetically determined characteristic

genotype

particular allele of an organism

phenotype

what an organism looks like as a consequence of the interaction of its genotype and the environment

homozygous

two alleles that are the same for a particular trait

heterozygous

two alleles that are different for a particular trait

dominant allele

an allele that produces the same phenotype whether its paired allele is identical or different

recessive allele

an allele that produces its characteristic phenotype only when its paired allele is identical

karotype

23 sets of chromosomes, an individual's complete set of chromosomes

mutation

alteration to the nucleic acid sequence of a genome of an organism

asexual reproduction

reproduction without gametes, offspring are usually genetically identical

genetic variation

genetic differences within organisms of a population

artificial selection

choosing to breed different animals or fruits to achieve a desired outcome

natural selection

breeding happens naturally

complementary base pairing

bases in DNA can only pair with their complementary base- AT and GC

autosome

all chromosomes in a cell other than sex chromosomes

chromatid

one of two identical strands into which a chromosome splits during mitosis

mitosis

cell division in which the nucleus divides into nuclei containing the same number of chromosomes

meiosis

cell division that produces reproductive cells in sexually reproducing organisms

gamete

a mature sexual reproductive cell having a single set of unpaired chromosomes

homologous chromosome

homologous chromosomes have the centromere in the same position and genes for characteristic

alkali metals

form 1+ ions, extremely reactive, react violently with water

alkali earth metals

act in a less reactive way to alkali metals, form 2+ ions

group 14

includes metals, non metals and metalloids, many elements exist in allotropes

halogens

form -1 ions, found in salts rather than pure forms, get bigger and less reactive down the group, form molecules of 2 atoms

noble gases

stable and only react under extreme circumstances, colourless and occur naturally in the atmosphere, get denser down the group

exothermic reaction

a chemical reaction that releases energy in the form of light or heat

endothermic reaction

a chemical reaction that absorbs heat, feels cold

combustion

any chemical reaction in which a substance burns in oxygen gas to produce light and heat

hydrocarbons

substances that are made of only hydrogen and carbon atoms eg. methane

incomplete combustion

combustion is incomplete when there is limited oxygen supply and produces carbon monoxide

corrosion

a state of deterioration in metals caused by oxidation or chemical action

decomposition reaction

decomposition reactions are when a single reactant breaks down to form several products, general equation XY→ X + Y

thermal decomposition

when a substance decomposes when heat is applied

combination reaction

when two or more reactants combine into one product

precipitation reaction

when two soluble reactants combine to form an insoluble product known as the precipitate

ionic compound

contain ions and are held together by the attractive forces among the oppositely charged ions, are often metals and non metals

neutralisation reaction

reaction between an acid and a base which produces a salt and water

acid

any substance which produces H+ ions when dissolved in water and turns litmus paper red

base

any substance which produces OH- ions when dissolved in water and turns litmus paper blue

salt

ionic compounds that are produced with a chemical reaction with an acid

acid and metal reaction

acid + metal -> salt + hydrogen

acid and carbonate reaction

acid + carbonate -> carbonate salt + water + carbon dioxide

effect of temperature on a reaction

increases the speed of particles in liquid or gases so they collide more frequently and increases the energy in particles so that they collide harder and bonds are more likely to break

effect of concentration on a reaction

increases the rate of reaction- particles are more likely to collide when there are more of them

effect of agitation on a reaction

stirring- ensures that the reactants are kept in contact and removes build up of products around the reactants

effect of surface area on a reaction

possibility for reactants to react with it from multiple angles, which increases the rate of reaction

effect of catalyst on a reaction

reduce the amount of energy required to convert the reactants into the products and make it easier for reactants to collide

evolution

change in proportion of a particular genotype of a species over many generations due to environmental selection of a particular phenotype, forming a new species

homologous structure

characteristics that have the same basic structure eg. cat paw and lion paw, and have the similar ancestors

analogous structure

structures that look similar on genetically different organisms even though they do not share an ancestor

natural selection

the process where an environmental factor acts on a population and results in some organisms having more offspring than others

selective agent

the environmental factor that acts on a population

biotic factor

a factor relating to living things eg disease or lack of food

abiotic

a factor unrelated to living things eg drought

displacement

straight line distance between two points

average speed

the overall speed of an object excluding changes in speed over a journey

instantaneous speed

the speed of an object at a particular instant

air resistance

the friction between air and an object

gene splicing

the process used to add a gene into or remove genes from DNA

gene therapy

replacing a defective gene with a normal gene

genome

the genetic information carried by a haploid set of chromosomes

plasmid

a ring of DNA found in bacteria

recombinant dna technology

technology that allows dna to be recombined with other genes

adult stem cells

cells that can make certain types of body cells

embryonic stem cells

cells found in the embryo that are pluripotent

pluripotent

cells that are capable of becoming any type of cell in the human body

fossil

the preserved evidence in rocks or soils of organisms that once existed on earth

how are fossils formed?

when sediment builds up over the remains of an organism so that it does not decompose

original fossil

when a part of the organism is preserved with its chemical composition being the same as when it was living

replacement fossil

when the organism has chemically changed into another mineral

carbon film fossil

occur when the dead body partially decays and leaves a black deposit of carbon but none of the organism actually remains

indirect fossil

not part of the organism but are preserved forms of things such as footprints or fossilised dung

permafrost fossil

organisms that cause decay cannot grow in permafrost

fossil mould

imprint of the outside of the body in rock

amber fossil

when plant sap or gum has turned solid and small creatures get stuck in it

tar fossil

when oil seeps out of the ground onto the surface and organisms get trapped

peat

partly decomposed remains of plants, oxygen and bacteria are not found in the lowest layers of peat

dry air fossil

extremely dry conditions prevent bacteria from causing decay

relative dating

compares the age of one fossil or rock with another to determine which is older

which two facts does relative dating rely on?

sedimentary rocks forming in layers and that fossils are the same age as the rocks they are found in

layer by layer

sediment always settles, therefore the fossils at the bottom layers of sediment are always the oldest

strata

layers of sedimentary rock

index fossils

a fossil that is useful for dating and correlating the strata in which it is found

fluorine analysis

compares the amount of fluorine in different bones found in the same rock

radioactive dating

measurement of the amount of radioactive material that a fossil contains, uses the natural rate of decay of radioactive isotopes to estimate the age

big bang theory

theory that the universe began with a colossal explosion 114 billion years ago and has been expanding since

evidence that supports the big bang theory

cosmic microwave background and red shift

cosmic microwave background

a type of radiation that remains since the explosion millions of years ago and fills the whole universe

red shift

light from stars moving closer is blue, while stars that move further away appears red, shows that the energy from the explosion is spreading stars apart

species

two organisms which can breed to produce fertile offspring

speciation

the process by which one species splits into two or more separate species

three steps of speciation

variation, isolation, selection

evidence for evolution

fossils, distribution, comparative anatomy, dna and protein analysis, embryology

nuclear reaction

a process in which the nucleus of an atom is changed by being split apart or joined with the nucleus of another atom

alpha decay

when the nucleus ejects alpha particles consisting of two protons and two neutrons