Functioning systems Flashcards
multicellularity
- multicellularity means that the functions necessary to maintain life are shared between different specialised cells.
- cells work cooperatively for survival and reproduction
what makes organisms multicellular?
- cells (except gametes) must have the same DNA.
- cells must be connected, communicate and cooperate to function as a single organism.
-must have specialised cells - cells must be dependant on each other
advantages of multicellularity in plants
- more energy efficient & longer lifespan
- sexual reproduction
- variation in population
- complex responses to external stimuli
disadvantages of multicellularity in plants
- more energy required for survival
- cells cannot function independently
- more energy required for sexual reproduction
- populations take longer to evolve
levels of organisation in animal cells
organisational level of cells:
- specialised cells
- tissues
- organs
- systems
- organism
cell specialisation
- all multicellular organisms begin as a single cell (zygote) from the fusion of gametes
- the zygote develops into a multicellular embryo via mitosis
- continued cell division, resulting in multicellular organism and trillions of specialised cells
define cell differentiation
unspecialised cells (stem cells) become specialised cells
cell differentiation
- stem cells originate in blastula (blastocyst in mammals)
> make up germ layers & differentiate to form specialised cells (tissues & organs)
what are the three germ layers
- endoderm (internal) > lung, digestive & thyroid cells
- mesoderm (middle) > cardiac & skeletal muscle, RBC’s
- ectoderm (external) > neuron on brain, pigment cells
differentiation in animals
adult stem cells and only occurs in some tissues
differentiation in plants
- meristem tissue (at tips of shoots and roots)
- apical meristem (organs and root growth)
what is gene expression
the process where the information stored in genes is used to build different structures in a cell
features of gene expression
- determines how cells differentiate & function
- specialised cells:
> some genes are expressed / ‘switched on’
> some are not expressed / ‘switched off’ - eg. specialised pancreatic cells express the genes needed to produce insulin
levels organisation in vascular plants
- specialised cells
- tissues
-organs - systems
-organism - eg. angiosperms, conifers, cycads, ferns, ginkoes
functions of specialised cells in vascular plants
- transport of nutrients
- transport of H2O
- acquiring energy via photosynthesis
functions of specialised tissues in vascular plants
- involved in transport of H2O and nutrients
> xylem (H2O from roots)
> phloem (sugars and other organic compounds)
functions of specialised organs in vascular plants: roots
- absorb & store H2O and nutrients from soil
- support- anchor the plant to the ground
Stems:
functions of specialised organs in vascular plants: stems
- support the plant
- transport H2O and nutrients (+ stores)
- grow new plant tissue
> dermal tissue (outer layer)
> ground tissue (inner layer- non-vascular tissue)
> vascular tissue
specialised organs in vascular plants: leaves
- made up of: upper and lower epidermis and mesophyll
- vascular tissue (xylem and phloem) = veins in leaf structure
- photosynthesis
- epidermis (upper): covers entire leaf, secretes the waxy cuticle, no chloroplasts
- epidermis (lower): regulates gas exchange and H2O loss
C3 plants
- account for 95>% of plants
- photosynthesis occurs in mesophyll cells
- 3 carbon molecules produced by CO2 molecule
> calvin cycle - follow photosynthetic pathway with stomata open
C4 plants
- more complex photosynthetic process that C3 plants
- occurs in mesophyll & bundle sheath cells
- no photorespiration
specialised organs in vascular plants: flowers & friuts
FLOWERS:
- assist with fertilisation of ovules (in ovaries) by sperm (in pollen)
- specialised structures
> attract pollinaters
> create pollen for wind or water dispersal
FRUITS:
- protect the developing seeds
- help seeds disperse away
> attach to fur on animals for dispersal
equation for photosynthesis
6CO2 + 6H2O –> C6H12O6 + 6O2
equation for cellular respiration
C6H12O 6 + 6O2 –> 6CO2 + 6H2O + ATP