Biology unit 2

Pregunta	Respuesta
Respiration	a series of reactions in which energy is released from glucose.
Aerobic respiration	the reactions involved in breaking down glucose using oxygen, to release energy. carbon dioxide and water are produced.
aerobic equation	glucose + oxygen → carbon dioxide + water (+ energy)
where does aerobic respiration happen?	Most of the reactions involved happen inside mitochondria, tiny objects inside the cytoplasm of the cell. The reactions are controlled by enzymes.
The ways in which energy released from respiration is used by organisms?	- organisms us energy to build up larger molecules from smaller ones. (proteins and amino acids) - animals use energy to allow their muscles to contract (they can move) - mammals and birds use energy to keep their body temperature steady - plants use energy to build sugars, nitrates into amino acids, which are then built up into proteins.
physical activity increases...?	- increases tour breathing rate and makes you breathe more deeply to meet the demand for extra oxygen. - increases the speed at which the heart pumps to make your blood flow more quickly, developing more oxygen and glucose to cells for respiration, and taking more CO2 away.
the fitter toy are...?	- the lower your resting heart rate - the lower tour increase in heart rate during exercise will be - the shorter your recovery period will be
glycogen	a molecule that acts as a store of glucose in liver and muscle cells.
what happens during vigorous exercise?	muscles use glucose rapidly, so some of the stored glycogen is converted back to glucose to provide more energy. glycogen -> glucose -> (respiration) -> energy
anaerobic respiration	the incomplete breakdown of glucose, which produces lactic acid. it takes place in the absence of oxygen.
anaerobic equation	glucose -> energy + lactic acid
lactic acid	the product of anaerobic respiration that builds up in the muscles cells and can cause muscle fatigue.
cramp	is the build up of lactic acid, caused by a lack of oxygen yo your muscles. muscles can't respire using oxygen (aerobic), so muscles have to respire without oxygen (anaerobic)
how to get rid of cramp	restore the blood supply to the muscles, oxygen can combine with the lactic acid to produce CO2 and H2O. lactic acid + oxygen -> co2 + h2o
oxygen debt	the extra oxygen that needs repaying after anaerobic respiration in order to oxidise the lactic acid which has built up in the muscle cells.
DNA	the molecule in cells that stores genetic information, found in the nucleus in really long molecules called chromosomes. double helix structure.
gene	section of DNA found on chromosomes. contain instructions needed to make a specific protein.
how do cells make proteins	By stinging amino acids together in a particular order. DNA determines what proteins the cell produces, and what type of cell it is.
DNA fingerprinting	it is a way of cutting up a persons DNA into small sections and then separating them.
chromosomes	a long molecule of DNA found in the nucleus.
the bases that always go together	A & T G & C
mitosis definition	when a cell reproduces itself by splitting to form two identical offspring.
uses of mitosis	- when plants and animals want to grow - when plants and animals need to replace cells that have been damaged - in asexual reproduction
asexual reproduction	where organisms reproduce by mitosis to produce genetically identical offspring.
what happens during mitosis?	1. begins with a single cell 2. first cell makes a copy of each chromosome then it divides 3. each new cell has a full set of chromosomes and is identical to the original cell.
meiosis definition	produces cells which have half the normal number of chromosomes. only happens in the reproductive organs.
uses of meiosis	- in humans it only happens in the reproductive organs so these are where gametes are produced
what happens during meiosis	1. meiosis begins with a single cell 2. first the cell makes a copy of each chromosome 3. now there are two stages of cell division 4. 4 new cells are made, 23 chromosomes in each.
allele	an alternative version of a gene,
dominant allele	the allele for the characteristic thats shown by an organism if two different alleles are present for that characteristic.
recessive allele	an allele whose characteristic only appears in an organism if there are two copies present.
homozygous	where an organism has two alleles for a particular gene that are the same.
heterozygous	where an organism has two alleles for a particular gene that are different.
stem cell	an undifferentiated cell which has the ability to become one of many different types of cell.
embryonic stem cells	leftover 3 day old embryos that otherwise would be discarded from fertility clinics. created and exist entirely outside the body.
adult stem cells	rare cells, found in only some developed organs or tissues e.g bone marrow. have been successfully used for some time now in bone marrow transplants.
cystic fibrosis	is an inherited disease that affects many body organs, particularly the lungs and digestive system.
what happens in cystic fibrosis	it is caused by a recessive allele. organs become clogged up by thick, sticky mucus, which stops them working properly. many people are infertile. people have problems with digesting food - take enzyme pills.
cystic fibrosis - symbols for the different form of this gene	c = cystic fibrosis allele C = normal allele cystic fibrosis genotype = cc
polydactyly	when babies are born with extra fingers or toes. caused by a dominant allele. inherited form one parent who has the condition.
sex chromosomes - male and female XX XY	- they determine whether your male or female - all men have an X and a Y chromosome : XY the Y chromosome causes male characteristics. - all women have two X chromosomes : XX the combination allows female characteristics to develop.
who was Gregor Mendel?	- Austrian monk - noticed how characteristics in plants were passed on from one generation to the next
Mendels conclusions	1. characteristics in plants re determined by 'hereditary units'. 2. hereditary units are passed on from both parents, one unit from each parent. 3. hereditary units can be dominant or recessive - if an individual has both the dominant characteristic will be expressed.
genotype	what alleles you have e.g you could have the genotype Bb for hair colour.
phenotype	the characteristic you have, e.g brown eyes, blond hair..
monohybrid cross	when you cross two parents to look at the inheritance of just one characteristic controlled by a single gene.
embryonic screening	genetic analysis of a cell taken from an embryo before its implanted into the uterus during IVF, in order to check the embryo doesn't carry any genetic disorders .
pre-implantation genetic diagnosis (PGD)	during IVF before the embryos are implanted they remove a cell from each embryo and analyse its genes to see if its healthy or faulty which are then either kept or destroyed.
chorionic villus sampling (CVS)	carried out between 10-13 weeks of pregnancy. taking a sample of cells from part of the placenta to analyse their genes, if it has a genetic disorder parents can decide whether to terminate the pregnancy.
arguments for screening	- helps stop people suffering from certain genetic disorders - reduce healthcare costs - during IVF most of the embryos are destroyed anyway - gives parents a choice
arguments against screening	- it can be abused to get a desirable baby - implies people with genetic disorders are undesirable - unethical - CVS might cause miscarriage
what are fossils?	the remains of an organism from many years ago, which is found in rock.
fossil record	the history of life on earth preserved as fossils.
ways in which fossils form	1. from gradual replacement by minerals. 2. from casts and impressions. 3. from preservation in places where no decay happens.
how fossils are formed	fossils are formed from the hard parts of animals or plants which don't decay easily. e.g bones, shells, teeth, tough plant fibres
why is there a lack of evidence in how life first started on earth?	- scientists believe many early organisms were soft-bodied and soft tissue tends to decay away completely without forming fossils. - fossils that did form millions of years ago may have been destroyed by geological activity - incomplete fossil record
what is extinction?	the process by which a species dies out
reasons for species becoming extinct	- the environment changes too quickly - new predator kills them all - a new disease kills them all - can't compete with new species for food - catastrophic event happens that kills them all e.g collision with an asteroid - new species develops
a species	is a group of similar organisms that can reproduce to give fertile offspring
speciation	is the development of a new species
isolation	is where populations of a species are separated. this can happen due to a physical barrier.
natural selection	1. each population shows variation because they have a wide range of alleles. 2. in each population individuals with characteristics that make them better adapted to their environment have a better chance of survival and so are more likely to breed successfully 3. the alleles that control the beneficial characteristics are more likely to be passed on to the next generation.

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	Creado por Laura Heester hace alrededor de 8 años