Science Exam revision

Human Biology and Physics

Newtons first law

States that an object in motion will remain in motion until acted upon by an external force.

e.g. student and bus moving at the same velocity

when stopped he had the tendency to continue forward due to inertia

Newtons second law

• When a force acts on an object it will accelerate.

• F = ma

• Same force applied → different outcomes depending on mass.

• Increased mass results in a smaller acceleration (inverse relationship).

Newton's Third Law

• Every action has an equal and opposite reaction.

• Forces are the same size.

• Forces act in opposite directions.

Energy Efficiency

Input: 240 J

Useful output:

• 200 J (light)

Wasted output:

• 40 J (heat)

Efficiency formula:

efficiency = useful energy output/total energy output x100

Speed Conversions

m/s to km/h

Multiply by 3.6

km/h to m/s

Divide by 3.6

Quantities Vector and scalar

vector

• Size and direction

Scalar

• Size only

Pedigrees

Dominant

• Every generation

• Both affected parents can produce unaffected offspring

• (Aa / AA)

Recessive

• Can skip generations

• Two unaffected parents can produce affected offspring

• (Aa)

3 Enzymes

Helicase

• Unzips DNA strand

Polymerase

• Pairs free nucleotides

• Exposed bases through complementary bases

Ligase

• Seals the phosphate backbone

DNA Replication

• Semi-conservative

• One daughter strand, one parent strand

• Original strand acts as a template

DNA Structure

• Hydrogen bonds

• Phosphate-sugar backbone

• Nitrogen bases

• Complementary base pairs:

  • A – T

  • G – C

Speciation

Sympatric Speciation ("same")

• They choose to split up by preference

• Shrimp like high tide

• White clams like low tide

Allopatric Speciation ("away")

• Split by a geographical barrier

Stages of mitosis (Somatic cells)

Prophase

• Membrane disappears

• Chromosomes condense

Metaphase

• Chromosomes line up across the central axis

Anaphase

• Chromosomes travel to opposite poles

• Sister chromatids separate

Telophase

• Nuclear membrane forms around each new set of chromosomes

Purpose: Growth and repair

Where is DNA found?

DNA is found in the nucleus of cells.

What is the structure of DNA?

DNA is a double helix made of nucleotides.

Each nucleotide contains:

• Phosphate

• Sugar (deoxyribose)

• Nitrogen base

Explain the relationship between DNA, genes and chromosomes.

DNA is the molecule that carries genetic information. Genes are sections of DNA that code for proteins. Chromosomes are long strands of DNA containing many genes.

What is the function of DNA?

DNA stores genetic information and instructions for making proteins.

Describe DNA replication.

DNA unzips and each strand acts as a template. Complementary nucleotides are added to form two identical DNA molecules.

What is a gene?

A section of DNA that codes for a protein.

What is an allele?

A different form of a gene.

Example:

• B = brown eyes

• b = blue eyes

Difference between genotype and phenotype

Genotype

Genetic makeup (BB, Bb, bb)

Phenotype

Physical characteristic (brown eyes)

Difference between dominant and recessive alleles

Dominant

Expressed when present.
Example: B

Recessive

Only expressed when two copies are present.
Example: b

Difference between autosomal and sex-linked inheritance

Autosomal

Gene is on a non-sex chromosome.

Sex-linked

Gene is on the X or Y chromosome.

Sympatric Speciation and Allopatric Speciation

Sympatric

Species split while living in the same area due to behavioural differences.

Allopatric

Species split because a geographical barrier separates populations.

Forms of Kinetic Energy

• Movement

• Light

• Heat

• Sound

• Electrical

Forms of Potential Energy

• Gravitational

• Elastic

• Chemical

• Nuclear

What is energy transfer?

Energy moving from one object to another.

Example:
Heat moving from a hot cup to your hand.

What is energy transformation?

Energy changing form.

Example:
Electrical → Light → Heat

What is friction?

A force that opposes motion and often causes energy to be wasted as heat.

Meiosis

Purpose:

• Produces gametes (sperm and eggs)

Produces:

• Four genetically different cells

Includes:

• Two cell divisions