Science Semester 2 Exam

What is evolution?

The change in genetic traits of a population over generations

What is a population?

A group of individuals of a single species that live and interact in a specific area

Where does evolution occur?

Evolution occurs in populations not in individuals

What does variation within a population mean?

A measure of genetic differences that occur within a population

What are the 4 main mechanism of evolution?

• Mutation

• Gene Flow

• Genetic Drift

• Natural selection

What does muation mean?

New alleles arise because of small random changes in the DNA squence to produce new variations of a trait

What does gene flow mean?

The migration of individuals from one population to another (of the same species) to introduce new phenotypes

What does genetioc drift mean?

Changes im population due to random changes/chance events.

What is geological time?

Used to represent the history of teh earth and how it changes overtime

What does CO2 do in water

CO2 dissolves in water to make it more acidic decreasing its pH

What is biodiversity?

The variety of life on earth

What is species diversity

The number of different species within an ecosystem (visible)

What is genetic diversity

The range of genetic variations within a species (invisible)

What is a species?

Organisms able to produce fertile and viable offspring

What is the role of evolution generating biodiversity?

Result from interactions between organisms and their enviroments and the consequences of their actions over long periods of time

What is extinction?

When all members of a species die out

What are some factors that cause extinction?

Asteriod impact, Climate change, Volcanic activity, Sea level chnage, Glacial cycles. They are increased by human activity

What is mass extinction?

Mass extinction is when lots of things go extinct

Why is it important to maintain genetic diversity/biodiversity in populations?

In an ecosystem everything is interconnected, if biodiversity is low the loss of 1 species might place an entire ecosystem at risk

What is adaptation

A genetic trait of an organism which increases its likihood of survival in its enviroment

What is structural adaptations

Visible and external deatures of an organism eg body coverings, limb specialistations and sensory organs

What is behavioural adaptations

The things an organism does that helps it survive and trhive and must be observed over a long period of time to be seen. eg: Communication, Social and Territorial interactions, Mating behaviours, Obtaining food

What is physiological adaptations

Is invisible and internal, it refers to the way an organism responds on a cellular and molecular level eg: Regulating water balance, nutrient balance, reproductive stratergies, sensing and processing of sensory information

What is natural selection

The main mechanism for evolutionary change. Where the fittest organism survives and the weaker organism is less common in the population

What are the 4 steps of natural selection?

1. Variation in population

2. Selective pressures

3. Selective advantage (survival of the fittest)

4. Reproduce and pass on favourable traits

How does natural selection relate to adaptations

Evolves through natural selection, this occurs in step 4 of natural selection when adults reproduce. Over time tehy become better adapted to the enviroment

What are the 4 stages of speciation

1. Common ancestral population

2. Geographical isolation

3. Different selection pressures

4. Reproductive isolation

5. Generations

What is reproductive isolation

When geographical barriers are removed and different groups are unable to interbreed to produce viable offspring as they have become different species

What is speciation

The process by which a new species is formed from an orgianl ancestral species

What is artifical selection/selective breeding

Involves humans selecting individuals that have teh most desirable phenotypes and exclusivly breeding these individuals

What is the difference between natural selection and artifical selection

Natural selection is nature selecting what best fits teh enviroment while artifical selection is humans selecting what best fits their needs and wants

What are some common examples of artifical selection

Dog breeding, chickens to make them fat and creating leafy vegtables from a weed

What are some issues relating to artifical selection

Reduces genetic diversity

Often contridIcts natural selection

Can cause new mutations

How do fossils provide evidence for evolution

They are remains or traces of past organisms many of which are extinct so we can see what the previously looked like

What are the circumstances that must be met for fossilation to occur

1. Death and Decay

2. Rapid burial by sediment

3. Permineralization (mineral deposits form an internal cats)

4. Erosion and exposure

How can fossils be dated using stratigraphy?

Also known as relative dating, teh deeper teh fossil the older the fossil and the more simple the organism the older it is

What is absolute dating

A precise estimation of a fossils age through tehe use of the amount of Radioisotopes such as carbon 14 left in the body

How do you calculate half lives

Continusly half 100% until you get to the fraction provided then using the length of a half life you can work out how old teh fossil is

How can comparing anatomy provide evidence for evolution

Similarties in the structural features of organisms provides evidence of how speices have changed overtime

What is a analogous structure

Structures that serve the sane function in a different organism due to similar enviromental pressures that are structurally different and there is no recent common ancestor eg birds and butterflies having wings

What is a homologous structure

Structures in different species which are similar due to being inherited from a recent common ancestor.

How can comparartive embryology provide evidence for evolution?

Similarties in developing embryos of different species suggesting a common evolutionary ancestor and common genes

What is bigoegraphy?

The study of the geographical distribution of organisms this results in organisms being seperated and forming new species

How can comparing DNA and protiens be used as evidence for evolution?

Comparing similarties in the molecules that make up organisms, the more similar the molecules of 2 different speices the more closely related they are.

How do you interpert evolutionary trees?

From left to right, each branch point represenys a shared ancestor between groups of species

Basic structure of an atom

3 basic particles of neutrons, protons and electrons. Protons and neutrons in the nucleus and electrons in electron shells.

Where are metals, metalloids and non-metals on the periodic table

Metals are on the left side and middle, non-metals on the right and metalloids on a staircase starting at boron and ending at tellurium

What are valance electrons and shells

Shells are the outer most electron shell and electrons are electrons in the outer shell of an atom

Shell capacity for the first 20 elements

1st - 2, 2nd - 8, 3rd - 8, 4th - 8

What is the organisation of the Periodic Table

Organised in rows called periods and organised by increasing atomic number and colums called groups and have similar properties

What are elements

Pure substances made of only 1 type of atom, they cannot be broken down

What are compounds

Substances made of 2 or more elements chemically combined, they can be broken down into simpler substances. This means they have different properties from their elements.

What are covalent bonds

Formed when 2 or more non-metals share electrons creating a stable balance of attractive and repulsive forces between atoms

What are ionic bonds

Formed when a meatl transfers its valance electrons to a non-metal creating cations and anions to create a full valance shell

How are cations and anions formed

Formed when a metal gives a valance electron to a non-metal to achieve a full valance shell so the metal has more protons than electrons and the non-metal has more electrons than protons

Key properties of ionic compounds

Typically high melting/boiling points, often solid, conduct electricity when dissolved and generally soluble in water

How do you name an ionic compound

Naming substances by writing the cation first and anion second but the suffix of the second is ide

How do you name an covalent compound

Using the ionic formula but adding a prefix at the beginning of each word

What is the law of conservation of mass

Matter/mass cannot be created nor destroyed the mass of the reactants should be equal to that of the products

Where are reactants and products in an equation

Reactants on the left and products on the right

What are precipitation reactions

When 2 soluble ionic solutions mix to form an insoluble solid product (precipate) and an aqueous solution

What is a general equation for precipitation reactions

AB(aq) + CD(aq) = AD(s) + CB(aq)

What is electron-proton attraction

Electrons are attracted to protons in the nucleus. Electrons in inner shells have a stronger attraction to electrons in the outer shells.

What is the octet rule

Any element which has a full valance shell will have a stable electron configuration, be unreactive and be found in its pure state. Other elements will try to fulfill this rule by gaining or losing electrons.

Octet rule for metals

If an atom has 1,2,3 valance electrons they will lose their valance electrons to empty their outer shell and become a cation

Octet rule for non-metals

If an atom has 5,6,7 valance electrons in the outer shell tehy will gain electrons to fulfill their outer shell

What is a solubility curve

It is produced when the solubility of a substance (measured in g/100g) is plotted againist temperature. Accuratly measuring the amount of solute in a solution at a particular temperature

What does unsaturated mean

A solution that contains less than the max amount of solute capable of being dissolved

What does saturated mean

a point of max concentration no solute is able to be dissolved

What does supersaturated mean

a solution that contains more than the max amount of solute able to be dissolved

What is an acid and their pH

Acids have more hydrogen than bases and react with bases to form hydrogen gas with a pH 1-6 with 1 being strong and 6 being weak

What is base and their pH

Base has more hydroxide than acids and react with acids to neutralise them with a pH 8-14 with 8 being weak and 14 is strong

What is the neutralisation reaction

When an acid and base are mixed together they neutralise and form a pH 7. Acid + base = water + metal salt

What are acid and metal reactions

Acid + metal = salt +hydrogen

Acids and metal carbonate reactions

Acid + metal carbonate = metal salt + water + CO2

Acids and metal oxides reactions

Acid + metal oxide = metal salt + water

What are reaction rates

A calculation of how fast a reactant turns into a product by measuring the quantity of reactant used or the product formed over time

What is collision theory

For a reaction to occur particles must collide at teh correct angle and with sufficent energy.

What is activation energy

Minimum amount of energy required to break bonds and form products

What are the factors that affect the rate of reaction

Affects the frequency of particle collisions and the amount of collisions with enough energy

• Concentration

• Surface area

• Temperature

• A catalyst

• Pressure

Increase concentration of reactants

Increases the rate of reaction as there is a greater number of particles

Increase temperature of reaction

Increases the kinetic energy of particles increasing frequency and proportion of particle collsions with the required energy to react

Increase surface area of solid reactants

Increases number of particles exposed and avaiable to react increasing frequency of particle collisions

Use of a catalyst in the reaction

Provides and alternate route with lower activation energy so particle collisions need less energy to occur increasing rate of reaction

Group 1 (Alkali metals) trends

Down the table low melting and boiling points decrease

React strongly with water to produce hydrogen gas and alkali solution (lower the stronger)

1 valance electron

Group 2 (Alkaline earth metals) trends

Low melting points but higher than group 1 and recat strongly with wtaer but less than group 1 producing hydrogen gas and alkaline solution (lower=stronger), 2 valance electrons

Group 17 (Halogens) trends

Down the table melting and boiling points increase, recat with metals to form salts. 7 valance electrons

Group 18 (Noble gases) trends

Boiling and melting points increase from He - Ar and decrease from Ar - Rn. Very unreactive, found in its pure state

Groups 3-12 (transition metals) trends

Generally high melting and boiling points which increase accross the period and decrease down a group. Much less reactive than groups 1 and 2 and reactivity increases down groups and decreases left to right. Generally ahve 2 valance electrons

Which is the most reactive element

Francium

What is the least reactive element

Flourine

What is teh radius of the atom

A measure of the distance from the centre of the atom to its outer most electron, it decreases across periods

What do greenhouse gases include?

Water, methane and carbon dioxide

How does the greenhouse affect affect life on earth

It moderates temperatures so life can survive

What is the difference between the greenhouse effect and the enhanced greenhouse effect

Greenhouse effect is the natural warming of the earths surface due to greenhouse gases which is essentail for life while the enhanced greenhouse effect is additional warming due to human activities including deforestation, urbanisation and burning fossil fuels increasing greenhouse gas concentrations

How do the movement of ocean and air currents affect global temperatures

They both move heat around the earth, ocean currents transport warm water from the eqautor to the poles and brings cold water back down. Air currents move heat from warm areas to cold areas and cold air to hot areas

What is permafrost

A frozen layer of soil which traps CO2

How does permafrost affect the levels of carbon dioxide in the enviroment

When permafrost melts it releases all of the trapped CO2 into the enviroment increasing the CO2 levels of the enviroment

How does melting polar ice affect sea levels

As the polar ice caps melt the water which is kept in them is released into the oceans