SB1i + SB3h - SB4c Flashcards
Diffusion
An overall movement of particles from an area of higher concentration to an area of lower concentration.
Concentration gradient
A difference between two concentrations. Particles diffuse down a concentration gradient.
The bigger the difference of concentrations, the steeper the gradient and faster the diffusion occurs.
What does diffusion allow?
Small molecules (such as oxygen and carbon dioxide) to move in and out of cells.
Partially permeable (semi-permeable) membrane
A membrane that allows some molecules through it and not others.
Osmosis
Diffusion of small molecules of a solvent, such as water, through a semi-permeable membrane. The overall movement of solvent molecules will stop when the concentration of solutes is the same on both sides of a membrane.
What can osmosis cause?
Tissues to gain or lose mass.
How do you calculate mass change?
(Final Mass - Initial Mass) / Initial Mass x 100
A negative answer is a % loss in mass
Active transport
Cells transporting molecules against a concentration gradient, or transport molecules which are too big to diffuse through the cell membrane
How is active transport carried out?
By transporting proteins in cell membranes. The transport proteins capture certain molecules and carry them across the cell membrane. This is an active process and so requires energy.
What kind of processes are osmosis and diffusion?
They are passive processes so they do not require an input of energy.
What are sex chromosones?
2 chromosomes that determine what sex you are.
What sex chromosomes do females have?
XX
What sex chromosomes do males have?
XY
What are punnett squares?
They are diagrams that show another way to demonstrate inheritance. The boxes show the possible genotypes.
What are punnett squares used for?
To work out the theoretical probability of offspring inheriting certain genotypes.
They are also used to work out the probability of different phenotypes caused by alleles.
Heterozygous
You have one recessive allele and one dominant allele.
Homozygous
You either have 2 dominant alleles or 2 recessive alleles.
Why must people be given the right blood type?
The blood that they are given must be of the right type otherwise the red blood cells in it will clump together, which can kill.
How do you classify different types of blood?
Blood is classified in the ABO blood group system. In this system, everyone’s blood is in one of the 4 groups A, B, AB and O.
How do you determine which blood group you have?
Which blood type you have is determined by certain “marker molecules” on the outside of your red blood cells.
Which of the markers are dominant and recessive?
Allele O is recessive to both A and B however a person with genotype AB shows the affect of both alleles.
Codominant
When both alleles for a gene affect the phenotype.
How are most human characteristics controlled?
By many genes, not just one. For example several genes affect eye colour in humans, however most variation in eye colour is caused by the OCA2 gene
Melanin
A protein that makes hair, eyes and skin darker in colour. Blue iris contains little melanin, while a brown iris contains a lot.
Mutation
A change in a gene that creates a new allele. They happen when there is a mistake in copying DNA in cell division.
The human genome project
In 2003 the first complete human genome was decoded. The project produced a map of 3.3 billion complementary base pairs in one set of 46 human chromosomes.
What can mapping a person’s genome show?
It can indicate their risk of developing diseases that are caused by different alleles of genes.
What is genetic variation?
Difference between individuals of the same species as a result of the variation of their genes.
How is genetic variation caused?
By the different alleles inherited during sexual reproduction. Different alleles are produced by mutations, some of which can cause changes in the phenotype.
Environmental variation
Characteristics affected by their surroundings, for example, how well plants grow is affected by how much light, water and nutrients it gets.
Acquired characteristics
Characteristics that are changed by the environment during the life of the individual. Such as piercing your ear.
Discontinuous variation
Where the data can only take a limited set of values.
Continuous variation
Where the data can be any value in a range
Normal distribution
Continuous data for variation often forms a bell shaped curve
Binomial system
Using 2 Latin words for naming species
Evolution
If the environmental conditions remain changed, natural selection occurs over and over again, and new species evolves with all the individuals having the better adapted variations.
How do scientists use fossils to track human evolution?
They work out how old the fossils are and put them in age older. The fossils do not show smooth changes over time because some have not been discovered.
What was discovered in 1992?
Scientists discovered some 4.4 million year old fossilised bones from a extinct human like species. More fossils from this species were found and nicked name Ardipithecus Ramidus.
Who is Ardi?
Ardi is the most complete set of bones of her species. Ardi was about 1.2m tall and 50kg. Her leg bones show that she may have been able to walk upright. She had very long arms though and very long big toes that stuck out of the sides of her feet and would have allowed her to climb trees.
What was discovered in 1974?
Australopithecus Afarensis (nicknamed Lucy). She lived 3.2m years ago and was about 1.07 metres tall. She could probably walk upright. Although her toe bones were arranged in the same way as those of modern humans, they were much more curved.
What did Mary and Louis Leakey discover?
They found a more recent human like species in the 1960s. They decided it was closely related to modern humans (homosapiens) and therefore named it Homo Habilis, which translates as handy man.
Homo habilis fossils are 2.4 to 1.4 million years old. The animals were quite short with long arms but walked upright
Homo Erectus
Discovered in Asia in the late 19th century and so many scientists thought that humans evolved in Asia. However an almost complete 1.6 million year old skeleton was found by Richard Leakey in 1984 in Kenya. This species was 1.79 metres and strongly built.
3.3 million years ago
The earliest evidence of human like animals using stone tools.
What did Charles Darwin and Alfred Russel Wallace come up with?
Essentially the same idea about how organisms evolve into each other. The first book about this idea was written by Darwin and published in 1859.
Natural selection
By chance the variation of some individuals make them better at coping with change than others and more likely to survive (also called survival of the fittest)
Inheritance
The survivors breed and pass on their variations to their offspring so the next generation contains more individuals with the better adapted variation.
Resistant
Not affected by
What happened with rats in the 1940s and 50s?
Warfarin was used to poison them. When it was first used most rats died but within 10 years most were resistant. Due to the genetic variation there had always been some rats that were resistant. As the poison killed the non-resistant rats, the only rats left to breed were resistant.
The pentadactyl limb
Vertebrates have limbs with five fingers.
