Topic 4 Flashcards
middle lamella function
outermost layer that acts like a glue to stick adjacent plant cells together
plasmodesmata function
- threads of cytoplasm which connect cytoplasm of neighbouring plant cells
- allows substances to be transported between plant cells + facilitates cell to cell communication
pits in plant cell
- thin regions of cell wall that facilitates transport of substances between cells
function of amyloplasts in plant cell
- small membrane bound organelles tht contain startch granules + responsible for storing starch + converting back to glucose when plant needs
what is the tonoplast
membrane around vacuole to control movements in and out of the cell
cellulose structure and function
- polymer of long beta glucose, joined by 1,4 glycosidic bonds
- due to inversion of beta glucose, lots of hydrogen bonds form between the long chains -> gives cellulose great strength
- its the main structural component of cell walls. high tensile strength allows it to be stretched without breaking so maks it possible for cell walls to withstand turgor pressure.
xylem structure
- lignified cell walls which van withstand the hydrostatic pressure
- no end plates which allows the mass flow of water as the cohesive and adhesive forces are not impeded
- dead cells which do not impede the transport of water and dissolved solutes
- pits in walls (non lignified sections) which allows for the lateral flow of water
function of xylem
transports water and minerals up the stem, and for structural support
structure of phloem
- living cells
- less cytoplasm
- perforated end walls called sieve plates
- lots of pores on sides, some that communicate via cytoplasm-filled pores called plasmodesmata, with an adjacent living cell called companion cell giving the phloem cells metabolic energy for the transport of sugar solution
function of phloem
transport of photosynthetic products and plant growth substances up and down stem and root
sclerenchyma fibres structure
- outside phloem
- dead cells and very thick cell walls
- heavily lignified and secondarily thickened but not in rings or spirals
- lumen is very small and maybe absent
function of sclerenchyma fibres
- thickened cell walls provide structural support
what are the properties of water that are important to plants
- polar molecule and a solvent
- has high specific heat capacity. hydrogen bonds between water molecules keep the temperature in water bodies fairly constant from season to season (allows living things to avoid rapid temperature changes)
- water molecules cohere so will stay as continuous columns in xylem. also means it has high surface tension which creates a skin that allows organisms like pond skaters to move on its surface. also adhesion of water molecules is important
Function of calcium ions
used in formation of calcium pectate in middle lamella which is the flue between plant cells and lack of it gives gnarled and mishapen leaves
what is sustainability
using resources in such a way that the requirements of current generations are met without depleting these resources for future generations
why should genetic diversity be maintained?
- reduced genetic diversity = reduced chance of adapting to environmental changes
roles of zoos in conserving endangered animals
- education abt illegal trade in animals and products, need for biodiversity and captive breeding programs
- scientific research on control of diseases, techniques to improve breeding
- captive breeding programmes increase numbers, reducing risk of extinction, maintain genetic diversity.
why are seeds rather than living plants stored
- less space required so more species can be held in available space
- most plants produce large numbers of seeds so collecting small samples is unlikely to damage wild population
- easier to store as dormant
why should u conserve rare plants
may carry genes that are used in crop plants to confer resistance to diseases and pests
seed collection and storage steps
- seeds collected from MANY individual plants so they are likely to have higher genetic diversity than seed from single plants
- seeds x rayed to check for fully formed embryos so allows only viable seeds to be selected for storage
- seeds dried to remove water as reducing water content increases length of time seed can be stored and remain viable
- seed is stored in the cold as reducing temp also increases length of time a seed can be stored and remain viable.
- then some seeds periodically germinated to check viability
- if less than 75% germinate, those that did are allowed to grow into mature plants tht produce their own seeds which are then stored
- if more than 75% germinate, remaining seeds are retained in cold storage and can be checked again for viability.
what are issues with seed banks
- stored specimens have to be replanted as they lose viability
- only some biodiversity can be stored
- certain seeds cannot be stored this way
- seed banks are expensive to build and run. power needed to be sustained to keep seeds v cold
benefits of conserving plants in seed banks
- conserves genetic diversity
- protection of the species of plants from natural disasters/effects from climate change
- the crop varieties in the seed banks may have traits that are useful in the future
- it also helps to ensure food security
- Cheaper than fully grown plant
- Larger numbers w/ less space
- Less labour required
- Can be stored in any cool dry place
- Less likely to be damaged from disease, natural disasters or vandalism
describe the cohesion tension theory
- water evapourates out stomata on leaves. loss of water volume = lower pressure
- when water lost by transpiration, more water pulled up xylem to replace it
- due to hydrogen bonds between water molecules, theyre cohesive creating column of water within xylem
- water molecules also adhere to walls of xylem = water column pulls up
- as this water column pulled up xylem, it creates tension = xylem pulled more in = it becomes narrower.
how can conservation programs help prevent extinction
- isolate them from other species
- select the best mate and increase the in threat species by having more offspring
- reintroduce them into the wild
Problems with reintroduction
- They may bring new diseases harming other organisms
- The organisms may not be able to survive in the wild successfully
contribution of zoos to scientific research
- Increases knowledge on behaviour, physiology and nutritional needs
Contributing to conservation methods - Can carry out research studies not possible in the wild
E.g. nutritional or reproductive studies - Educates the rest of the world so they are more interested
More willing to want the animals to be protected - Can educate local people on why they shouldn’t hunt/ kill them
E.g. learning elephants don’t like tomatoes in their eyes so tomato bombs are being used to deter elephants entering villages - Though animals in captivity may act differently to those in the wild
problems with zoos
- Animals may not be willing to breed outside of their habitats
- There might not be enough animals of a species to breed successfully
- Age, gender, health, siblings
- Many people think it’s cruel to keep them in captivity
william withering’s drug testing
- treated his patients with an extract made from foxgloves, which contains the drug digitalis
- foxglove is poisonous to humans, so he made different versions of his remedy containing different concentrations of digitalis
- these versions were called his digitalis soup
- He experimented on his patients to find the most effective concentration of digitalis that would treat dropsy without poisoning the patient
compare withering’s drug trial process to today’s drug trial process
- both trials used different doses (to determine safe
dose) - William Withering did not use healthy volunteers and
this drug trial did - William Withering did not use a placebo while this trial
did
explain how two species of snake could have arisen from common ancestor
- mutation leads to variation within the population of snakes
- natural selection led to those snakes which were better camouflaged surviving to reproduce
- therefore giving rise to two populations with differing allel frequency
- as a reult of natural selection, two populations became reproductively isolated
- sympatric speciation
