GCSE AQA Biology - Unit 2 Flashcards

Question	Answer
Why can't scientists be certain about how life began?	They don't have enough valid and reliable evidence.
What are fossils? How can they be formed?	The remains of organisms from many years ago which are found in ROCKS. They can be formed by the hard parts of organisms that do not decay easily 2) Or when parts of an organisms are replaced by other materials AS THEY DECAY 3) From parts of organisms that haven't decayed because one or more conditions needed for decay are absent 4) As PRESERVED TRACES of organisms, like footprints, burrows and rootlet traces
Many early forms of life were soft-bodied, which means they left ___ traces behind. What traces there were have been mainly ____ by _____ activity.	1) FEW 2) DESTROYED 3) GEOLOGICAL
We can learn from fossils how ___ or how ____ _____ organisms have changed as ____ ____ on Earth.	1) little 2) much 3) different 4) life evolved
EXTINCTION may be caused by:	1) new, more successful predators 2) the cyclical nature of speciation 3) change to the ENVIRONMENT over GEOLOGICAL TIME 4) sudden catastrophic disaster 5) new more successful COMPETITORS 6) new DISEASES
New species arises as a result of...	1) SPECIATION - populations become so different that interbreeding to produce fertile offspring becomes impossible 2) ISOLATION - Two populations of a species get separated e.g. geographically 3) GENETIC VARIATION - each population has a wide range of alleles that control their characteristics 4) NATURAL SELECTION - The alleles that control the characteristics which help the organism to survive are selected
Mendel proposed the ideas of separately inherited factors because?	- He observed that pure-breeding purple plants and pure-breeding white plants produced all purple pea plants instead of a blend of white and purple pea plants - He concluded that the purple colour must be dominant - He thought these was due to 'factors' which were later linked to CHROMOSOMES - Scientists didn't agree because they thought that inherited factors blended and Mendel was only a monk whose work was published in an obscure journal Note : monohybrid inheritance is when a characteristic is controlled by a single gene
Interpreting genetic diagrams	Image: Genetic Diagrams (image/png)
Alleles are what? Homozygous means what? Heterozygous?	Alleles are different versions of the same gene. If you're homozygous for a certain gene, then you carry two copies of the same allele Heterozygous for a certain gene = you carry two different alleles You have to be homozygous for the recessive allele to show Dominant shown even if heterozygous
Phenotype is the physical characteristics of an organism due to its genotype and environment Genotype - how a set of alleles determines the physical characteristics of an organism	TRUE
Embryo screening	1) Sperm and eggs mixed together fertilise. 2) Develop into embryos 3) One cell removed and analysed for defective allele 4) Healthy embryo implanted
Embryo screen evaluation	1) Abortion after testing the placenta for defective allele instead of embryo-screening can be more traumatic - risk of miscarriage Embryo screening - No need for abortion But: - Very expensive - May have surplus healthy embryos, unethical?
In body cells the ____ are normally found in pairs. Body cells divide by ______.	1) CHROMOSOMES 2) MITOSIS
The chromosomes contain...	genetic information
Mitosis process Mitosis occurs during ____	1) Copies of genetic material made 2) Cells divides once to form two GENETICALLY IDENTICAL BODY CELLS 1) Growth and to produce replacement cells
Sex cells only have one set of ..... Meiosis occurs in the ____ or the ____ in humans to form GAMETES.	1) chromosomes 2) testes and ovaries
Meiosis process	1) Copies of genetic info are made 2) Cells divides TWICE to form FOUR gametes each with a single set of chromosomes
Genetic diagrams are ____ models which can be used to predict the outcome of _____	1) biological 2) crosses
When gametes join at fertilisation, a single body cell with new pairs of chromsomes are formed. A new individiual then develops by this cell repeatedly dividing by ___	Mitosis
Most types of animal cells differentiate at an ____ stage BUT PLANT CELLS retain the ability to ____ throughout life. In mature animals, cell division is mainly ____ to ____ and replacement	1) restricted 2) repair
The cells of the offspring produced by ASEXUAL REPRODUCTION are produced by ____ from the ____ cells. They contain the ____ alleles as the parents.	1) MITOSIS 2) PARENTAL 3) SAME
Chromosomes are made up of ____ which has a double ___ structure.	1) DNA 2) helix
A gene is a small section of?	DNA
Are these genetic disorders caused by recessive or dominant alleles of the undesirable gene? i) Polydactyly ii) Cystic fibrosis	i) Dominant ii) Recessive so parents who are just carriers can pass it on to children
The chemical reactions inside cells are controlled by...	ENZYMES
Each gene codes for a particular combination of _____ ____ which make a specific protein	1) Amino acids
During ____ respiration, chemical reactions occur that:	- Use glucose and oxygen - Release energy
Most of the reactions in aerobic respiration take place in the mitochondria	TRUE
Energy released by respiration is used by the organism through:	1) Build larger molecules from smaller ones 2) In animals, to enable muscles to contract 3) In mammals and birds, to maintain a steady body temperature in colder surroundings 4) in plants to build up, sugar, nitrates and other nutrients into AMINO ACIDS which are then built into PROTEINS
1) During exercise the changes in your body are: 2) What effect do these changes have on your body	1) The heart rate increases - The rate and depth of breathing inc. 2) Increase the blood flow to the muscles - Increase supply of sugar and oxygen - Increase rate of removal of CO2
Muscles store glucose as what?	Glycogen which can then be converted back to glucose for use during exercise
Anaerobic respiration is?	Incomplete breakdown of glucose It produces LACTIC ACID

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GCSE AQA Biology - Unit 2 Flashcards

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	Created by Shreya Manna over 7 years ago