as 2020 1 and 2 Flashcards
why does convergent evolution occur
due to continuous variation of these species
why is the type of nuclear division in a zygote mitosis and not meiosis
mitosis is for growth; which needs genetically identical cells
explain the role of embryonic stem cells in the development of an embryo
-undifferentiated/ not specialised
-are a renewing source of cells/ can differentiate into any cell type
explain why cells of an inner cell mass of a blastula are not totipotent
-they are pluripotent
-not totipotent as cannot form a whole organism
-cannot give rise to extra embryonic tissue
-placenta not formed
why is collagen a fibrous protein
-only has two different amino acids
-has a structural function/ provides strength
-long chain of amino acids
-little/ no tertiary structure
-insoluble/ many non-polar amino acids
why is collagen so strong
-cross linking between adjacent molecules
-hydrogen bonds between polypeptides
-have staggered ends
describe the structure of the rough endoplasmic reticulum
-phospholipid molecules form a bilayer
-forming cisternae/ network of membranes/ flattened sacs
-covered on outside with ribosomes
-membrane continuous with nuclear envelope
explain the role of the membrane in the rough endoplasmic reticulum
-hold ribosomes/ enzymes in place
-compartmentalisation
-
when error bars are large, what does this mean
means that the standard deviation is spread out
describe the apoplast pathway
moves between/ along cell wall
explain how a specific molecule is used to show that two different species have evolved from a recent common ancestor
-sequence of amino aicds/ DNA bases/ RNA bases
-the smaller the number of differences between the molceule, the more closely related they are
what is a res of an SEM
5-50nm
how are erythrocytes specialised for their function
-space for o2 maximised
-flexible
-haemoglobin
-flexible shape
-transport O2/ CO2
-move/ squeeze through blood vessels
-large sa to volume ratio
how are neutrophils specialised for their function
-multilobed nucleus
-hydrolytic enzymes
-can change shape
-immune response
-destroy pathogens
-move to site of infection/ wound
-engulf pathogens
how are squamous epithelial cells specialised for their function
-flatterened shape
-thin
-fit together tightly
-for rapid diffusion
-at alveoli/ blood vessels
how are ciliated epithelial cells specialised for their function
-have cillia; hair like structures
-move/ beat in rhythm
-to move mucus/ trapped pathogens from lungs
why can members of the same family get a disease
it can be passed down in genes
what pathogen causes potato blight
prorocista
outline the action of agglutinins
-clump/join pathogens
-stop pathogens moving/ reproducing
-helps phagocytes then engulf multiple/ clumped pathogens
-phagocytosis of clumped pathogens
outline the process of vaccination to give an individual immunity
-a vaccine is produced that is a safe form of an antigen
-a small amount of vaccine is injected into the blood of the individual to be vaccinated
-antigen presentation occurs/ antigen bind to specific B/T lymphocyte/ cell
-clonal selection/ clonal expansion/ plasma cells produced/ produce antibodies- primary immune response
-memory cells/ secondary immune response
explain why vaccinating most of the pop reduces spread of an infection
herd immunity occurs
fewer people can catch/ spread virus/ measles or fewer vaccinated.
most people cannot catch or spread the virus
how are more precise results obtained
-repeats and calc mean
-use a biosensor to measure glucose conc
-more smaller temp intervals
-more regular time intervals
what is the role of cartilage in gas exchange
cartilage stops trachea/ bronchus from collapsing
what is the role of elastic fibres in gas exchange
elastic fibres allow for recoil of alveoli
how does ventillation occur in bony fish
-water enters mouth
-pressure/ volume change in buccal cavity
-water flows/ pushed over gills
-water leaves via operculum
-throughflow system/ one direction flow
how does bony fish gas exchange occur
-gill fillaments/ lamellae
-large surface area
-thin
-short diffusion distance
-good blood supply/ blood vessels
-steep conc grad
-counter current system
-tips of gill filaments overlap to slow down water transfer
how does ventillation occur in insects
-muscular movements
-abdominal pumping
-volume/ pressure change in abdomen
-thorac change in flight
-air drawn in or forced out
-size of spiracles changes
-large surface area to volume ratio= diffusion may be sufficient
how does gas exchange occur in insects
-gas/o2/co2 diffuses out of trachea
-oxygen dissolves in water at tracheoles
-diffuses into surrounding cells
-many tracheoles so large surface area
-spirals of chittin hold trachea open
