science quiz Flashcards
what are eukaryotic cells
cells that store their genetic material (DNA) in a nucleus, contain membrane-bound organelles, mitochondria and ribosomes which make proteins for the cell
example- plant and animal cells
what are prokaryotic cells
cells that contain their genetic material in small rings called plasmids, don’t contain membrane-bound organelles, contain ribosomes and are much smaller than eukaryotic cells
example- bacteria
what does culture mean in science
to grow microorganisms, such as bacteria, for scientific study
what is the nutrient jelly inside petri dishes that is used to produce cultures called
agar
what is aseptic technique used for
to avoid contamination of equipment and allow organisms to be investigated one at a time
what are pathogens
bacteria that cause disease
what is used to treat bacteria
antibiotics/ antiseptics
how do you calculate the number of bacteria present
final number of bacteria= initial number (1)*2^number of divisions
what is a light microscope
light shines up through a specimen and through lenses, where it bends to create an enlarged image
what are electron microscopes
microscopes with greater magnification and resolution that allow scientists to study cells in greater detail and expand understanding of sub-cellular structures
what is used to make organelles within a cell appear clearer
a stain
what is resolution/resolving power
the shortest distance between 2 points that can be seen as separate points
how to calculate magnification
magnification= size of image/ actual size of object
what is the function and adaptations of a sperm cell
function- fertilise egg
adaptations- tail, mitochondria
function and adaptations root hair cell
function- absorb water and mineral ions
adaptations- root hair (increases surface area), no chloroplasts
function and adaptations nerve cell (neuron)
function- send electrical signals around the body
adaptations- long axon, many dendrites
function and adaptations muscle cell
function- contract to move the body
adaptations- mitochondria, glycogen (to store energy), proteins
what is the process of gas exchange in the lungs
oxygen enters the lungs and diffuses into alveoli, carbon dioxide diffuses out of alveoli
what is alveoli
air sacks in lungs
what is diffusion
the spreading out of particles, resulting in net movement from an area of high concentration to low concentration. Occurs through selectively permeable membranes
what is a selectively permeable membrane
a membrane with small openings allowing small particles and gases to enter and leave it
how do you increase the rate of diffusion
increase temperature, increase concentration gradient, increase surface area
what is urea
a waste product made by cells which diffuses from cells into blood so it can travel to the kidneys and be excreted from the body
formula surface area to volume ratio
surface area/volume
how does size affect volume ratio
the bigger the organism the smaller the volume ratio
how does increasing temperature increase diffusion
there is an increase in pressure causing particles to move more rapidly
what is osmosis
the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
what is a hypertonic solution
one in which the external solution has a higher concentraton of solute than the cell
what is a hypotonic solution
one in which the external solution has a lower concentration of solute than the cell
what is an isotonic solution
external solution has the same concentration of solute as the cell
what is flaccid
when plant cells lose water (hypertonic)
what is turgid
plant cells gaining water (hypotonic)
what is shrivelled
animal cells losing water
what is lysed
animal cells gaining water
what is passive
movement of substances without requiring energy
what is active transport
movement of substances from a more dilute solution to a more concentrated solution, requiring energy from respiration
what is a gene
a small section of DNA that controls a characteristic of your body
what are alleles
different versions of genes
what is cell division used for in multicellular organisms
growth and reparation
what is cell division used for in unicellular organisms
to reproduce asexually
how does cell division work
cells increase in number by dividing into 2
process-
growth phase where the cell doubles its sub-cellular structures and DNA so it can split, mitosis- chromosomes are pulled apart to separate ends of the cell, splitting of the cell membrane into 2 diploid, identical cells
what are tumours
a mass of cells
what are benign tumours
a mass of cells contained in one area
what are malignant tumours
formed of cancer cells that invade other tissues and spread around the body forming secondary tumours
what is cancer
when cell division happens uncontrollably causing cell numbers to increase inappropiately
what is the zygote
cell formed through fertilisation
what are stem cells
cells capable of differentiating into specific cell types
where can stem cells be found
developing embryos- differentiate into all human cell types to develop a foetus
adult bone marrow- differentiate into different types of blood cells
meristems in plants- differentiate into al plant cells to develop a new plant
what are organisms
interdependent living things
what is a population
a group of organisms of the same species
what is a community
2 or more populations of organisms
what is a habitat
the place where an organism lives
what is an ecostystem
interaction between the community and abiotic aspects of their environemnt
what is biodiversity
variety of all the different species in an ecostystem
what does high biodiversity indicate
that an ecosystem is stable and not dependant on one species
what are quadrats used for
to measure the biodiveristy of a habitat by counting the abundance of different species
what is random sampling
used for investigating the number of organisms in a species, species diversity or percentage cover by placing quadrats at random coordinates
what is systematic sampling
used for investigating the effect of an abiotic factor by placing quadrats at regular intervals along a transect line
what does human population growth mean for biodiversity
more resources are used and more waste is produced
how do humans reduce land available
building, farming, deforestation, quarrying and waste disposal
how is peat formed
when dead plant material cannot decay because of the acidic and anaerobic conditions
why are peat bogs being destroyed
to provide garden and farming compost- releases C02 into the atmosphere
how can humans reduce their impacts on biodiversity
-breeding programmes for endangered species
- rare habitat protection
-reducing deforestation
-recycling resources to reduce landfill waste
-growing hedgerows on farms
what are the 3 types of pollution
air pollution, land pollution and water pollution
what is the processing and treatment of waste water
-screening and grit removal
- sedimentation (to seperate sludge and effluent)
- sludge is digested by specific bacteria
-effluent is treated by specific bacteria ad chemicals
what is eutophication
when fertiliser applied to crops leaches into nearby rivers and streams, causing a rapid growth in plants from its rich nutrients, which blocks sunlight for organisms beneath them meaning they can’t photosynthesise to produce oxygen and resulting in their death and being broken down by decomposers which use up the remaining oxygen and overall results in the water becoming a dead zone that can no longer support life
what are indicator species
organisms that tell us about the levels of pollution in an area through their prescence/abscence
what is global warming
rise in global temperatures due to greenhouse gases
what is climate change
overall change in weather over a long period of time
why is global warming increasing
more levels of carbon dioxide and methane in the atmosphere as a result of burning fossil fuels and deforestation (less trees to absorb C02 for photosynthesis)
what are consequences of global warming
melting polar ice caps, rising sea levels, flooding, extreme weather patterns, loss of habitats, changing breeding patterns, changing migratory patterns
what is a vector
a physical quantity that has both size and direction
examples-
-displacement
-velocity
-acceleration
-force
what is a scalar
a quantity that only has size
examples-
-distance
-speed
-energy
what is speed
distance covered per unit time
speed= distance/time
what is distance
the length of the path between 2 points
what is velocity
speed in a given direction
velocity= displacement/ time
what is displacement
how far an object is from its original position
what is a resultant force
the net force or the overall effect of all the forces acting on an object
what is a resultant vector
the combination of 2 or more single vectors
example- resultant force
how do you calculate resultant force when forces are acting in the same direction
sum of the 2 forces
what is internal energy
the total kinetic energy and potential energy of all the particles that make up a system
why do particles have kinetic and potential energy
particles have kinetic energy because they are always moving/vibrating
particles have potential energy because their motion keeps them separated
how does temperature increase affect internal energy
heating a substance increases its internal energy
2 WAYS-
-Kinetic energy increases, temperature increases, state remains constant
-Potential energy increases, temperature remains constant, change in state
how does the position of particles affect potential energy
the further apart the particles the higher the potential energy
in which state do particles have the greatest internal energy
in gases
what is conduction
thermal transfer by the vibration of particles
what state of matter does conduction take place in
in solids
how does conduction work
the particles in a solid are always vibrating. If the solid gets hotter, the particles vibrate more and collide with neighbouring particles until all the particles of the solid are vibrating faster, which increases the temperature
why are solids better thermal conductors than liquids and gases
because their particles are closer together
what is convection
thermal transfer where particles in a heated fluid rise
what state does convection take place in
fluids- liquids and gases
how does convection work
particles in a fluid gain kinetic energy when heated and move away from each other meaning they become less dense and rise. as they rise they cool down and the particles that were on top of them sink and take their place, forming a cycle called a convection current
what is radiation
a heat transfer that travels through a vacuum and doesn’t require particles to move
how does radiation work
a warm object emits infrared radiation as heat waves which is absorbed by another object to heat it
what colour objects absorb or reflect heat best
dark objects absorb the most heat
light/shiny objects reflect the most heat
what is specific heat capacity
the energy required to raise the temperature of 1kg of a material by 1 degree celscius
what is temperature
a measurement of the average kinetic energy of the particles in matter
what is heat
energy that flows from a warmer to a colder object
what does the temperature change of a material when heated depend on
the mass of the substance, the material it is made from and how much energy is transferred to it
what is the equation for specific heat capacity
ΔE=mcΔT
change in energy= massspecific heat capacity change in temperature
ΔE- J
m-KG
C- J/KG°C
ΔT-°C
what are the similarities between conduction and convection
they both involve particles gaining kinetic energy
how can energy be used
energy can be transferred usefully, stored or dissipated but never created or destroyed
how can unwanted energy transfers be reduced
- through lubrication (reduces friction that produces heat)
-Through tightening (prevents unwanted vibrations that waste energy through sound)
-Through thermal insulation (reduces heat loss)
what are the 4 energy transfers
- heating
-waves
-electrical
-mechanic
what is a system
an object/ group of objects
what is a closed system
one where no energy can escape/enter
the total energy never changes
what does it mean when something changes in a system
energy is transferred between its stores or to the surroundings
where does energy eventually end up
all energy is transferred to the thermal energy stores of the surroundings
what is latent heat
energy transferred when a substance changes state
what is specific latent heat
the energy required to change 1kg of a substance without changing the temperature
fusion- solid to liquid
vaporisation- liquid to gas
formula- E=mL
what is an element
a pure substance made up of only one type of atom
what is a compound
2 or more elements chemically bonded
what is a mixture
2 or more elements or compounds that can be physically separated, no chemical bond
what is a molecule
a group of atoms bonded together
how are atoms formed
they consist of a positively charged nucleus, containing protons (+) and neutrons, surrounded by electrons (-)
what is a nucleus
the dense, positively charged central part of an atom
what is the mass number
total number of protons and neutrons (on top of chemical symbol)
what is the atomic number
total number of protons (under chemical symbol)
what does the group number tell you
how many electrons are in the outer shell of an atom
what are ions
when atoms lose or gain electrons to form a full outer shell. They become stable but are no longer electrically neutral. Metal atoms lose electrons to form positive ions and non metal atoms gain electrons to form negative ions
what is resolution
the shortest distance between 2 points that can be seen as separate points
what are isotopes
atoms of the same element with different numbers of neutrons
what is relative atomic mass
the average value that takes account of the abundance of isotopes of the element
(mass no.abundance)+(mass no.abundance)
what are the noble gases
-elements in group 0 of the periodic table
-full outer shell- stable
-inert
-don’t easily form molecules
what are the alkali metals
elements in group 1
very reactive- increase in reactivity because the outer electron moves further away from the nucleus
soft, shiny, low melting/boiling points
what are the halogens
group 7
non metals
consist of diatomic molecules
melting/boiling points increase because the molecules become larger and the forces between them become stronger meaning more energy is needed
decrease in reactivity
what is relative atomic mass
average mass of the atoms of an element compared to the mass of carbon (12)
what is relative formula mass
the sum of the relative atomic masses of the element in a compound
calculation percentage by mass
% by mass= Ar*number of atoms/
Mr of compound
what is conservation of mass
matter cannot be created or destroyed, only transferred from one form to another
what is scientific uncertainty
there is a range of possible values in which the true value of a measurement lies
2 methods to estimate uncertainty-
- calculate mean
find range and divide by 2
mean +/- uncertainty (range/2) - half the smallest interval of the resolution of an instrument
what is a force
the push/pull on an object with mass which causes it to change its velocity
SI unit- newtons
what is the difference between contact/non-contact forces
contact forces need to be physically touching in order to act whereas non-contact forces act over a distance
what is speed
distance covered per unit time
speed= distance/time
SI unit- m/s
what is the difference between balanced and unbalanced forces
balanced forces- equal in size, opposite in direction, don’t cause a change in motion, resultant force 0N
unbalanced forces- can change the shape, speed or direction of an object, resultant force not equal to 0N
how is mass measured
in kilograms
how is weight measured
in newtons (N)
weight equation
W=m*gravity
difference mass and weight
mass is the amount of matter in an object and weight is the effect gravity has on that mass
what is velocity
how fast an object travels in a given direction
velocity= displacement/time
what is newtons third law
every action has an equal and opposite reaction. when 2 objects interact, they exert equal and opposite forces on each other. the forces are acting on different objects
explains how objects are able to move
how to calculate resultant force
if forces are acting in the same direction they are added, subtracted if acting in different directions and using a scale drawing if they are perpendicular
what is acceleration
the rate of change in velocity. can be an object speeding up, slowing down or changing direction. vector quantity
SI unit- m/s^2
acceleration formula
acceleration= change in velocity/ time
what is negative acceleration
deceleration
how does acceleration affect air resistance
as objects speed up air resistance increases
what is newtons first law
an objects motion will not change unless acted upon by an unbalanced force (a non 0 resultant force)
what is inertia
the tendency of objects to continue in their state of motion
what does a 0N resultant force mean
forces are balanced and the object is in equilibrium. The object will continue stationary if it is still and continue moving at the same velocity if in motion
what does a non- zero resultant force mean
the forces are unbalanced
a stationary object will accelerate in the direction of the resultant force
an object in motion will also accelerate in the direction of the resultant force
what is a gradient
the steepness of the slope at any point
straight line- constant gradient
curved line- gradient changes at every point
gradient can be positive (sloping upwards), negative (sloping downwards) and zero (horizontal)
gradient calculation
change in y/ change in x
