Exam Questions Unit 2- 2 Flashcards
what does species richness mean?
number/variety of a species
what does genetic diversity mean?
variety of alleles in a species/population
what are some factors that could decrease biodiversity? (7)
- hunting
- loss of habitat
- climate change
- competition
- disease
- emigration
- natural disaster
what are some factors that would increase biodiversity? (5)
- conservation areas
- wildlife reserves
- reintroduction
- breeding programmes
- immigration
What is the role of lignin in plant stems? (2)
- support
- impermeability to water
explain the term niche, using a named animal as an example (pangolin) (2)
- the role of an organism/species in its habitat/environment - the pangolin feeds on ants
examples of anatomical, behavioural and physiological adaptation (3)
anatomical= has a long tongue
behavioural= lives in hollow trees
physiological= secretes saliva
In what phase of meiosis does independant assortment take place?
metaphase I
Describe how independant assortment results in genetic variation (3)
- pairs of homologous chromosomes randomly line up along the equator of the cell
- this results in new/different combinations of chromatids
- and this then results in new/different combinations of alleles in the gametes
In what phase of meiosis does crossing over take place?
prophase I
describe the frequency of crossing over
it is proportional to the distance between the genes on the same chromosome
Why is it an advantage for cells with damaged DNA to be prevented from continuing through the cell cycle? (3)
- because DNA will be replicated in S phase
- and it prevents the formation of daughter cells with damaged DNA
- if the DNA is damaged then proteins will not function
Describe the appearance of a cell in metaphase (4)
- no nucleus
- chromosomes line up along the equator
- spindle fibres attach to centromeres
- centrioles (of animal cells) are at the poles
Explain the importance of the pollen tube nucleus, the RER and the Golgi apparatus in the production of extracellular enzymes needed for the growth of the pollen tube. (8)
Pollen tube nucleus=
- contains the DNA coding for the enzymes
- DNA is transcribed in the nucleus
RER= - ribosomes are involved in translation
- polypeptide chains become folded in the RER
- the polypeptide moves to the Golgi Apparatus in vesicles
Golgi Apparatus=
- polypeptide is modified in Golgi
- lysosomes form from Golgi
- exocytosis of enzymes out of the cell
What is the correct sequence of structures through which the pollen tube must grow before fertilisation can occur? (3)
- stigma
- style
- ovule
Describe the role of the male nuclei in sexual reproduction in flowering plants. (3)
- double fertilisation occurs
- one haploid male nucleus fuses with a haploid female nucleus to produce a diploid zygote
- one haploid male nucleus fuses with two polar nuclei to produce a triploid endosperm
Explain the importance of water to plants (5)
- dissolves ions
- acts as a medium for chemical reactions
- to transport minerals and ions
- provides electrons for photosynthesis
- regulates temperature by evaporation
Explain the importance of nitrate ions to plants (3)
- to produce proteins/DNA/amino acids/chlorophyll
- amino acids are then used for the synthesis of proteins
- chlorophyll is then used for photosynthesis
Describe the appearance of a plant with magnesium deficiency (2)
- yellow leaves
- smaller plant
why are there regulatory authorities relating to human embryo research? (3)
- to monitor research
- to monitor the source of the stem cells
- to prevent unethical use of the stem cells
Explain why chemicals from a whole heart are needed to produce mature heart cells from immature heart cells (6)
- chemicals switch on some genes
- differential gene expression
- genes coding for heart cell functions are switched on
- transcription occurs at active genes
- mRNA is used to produce proteins
- these proteins determine the function of mature heart cells
Suggest the advantages of using mature (heart) cells to test drugs developed for treating (heart) disease (3)
- these cells will function like (heart) cells
- use of animals is reduced
- clinical trials will not be carried out unless drugs are shown to be safe
Describe drug testing protocols that could be used to test drugs that are being developed to treat disease (3)
- in phase one the drug is tested on a small number of healthy people
- in phase two the drug is tested on a small number of patients with the disease, with placebo and double blind trials
- in phase three the drug is tested on a large number of patients with the disease, with placebo and double blind trials
