AOS2 Flashcards
level of organisation
Organism System Organs Tissue Specialised cells
all organisms need to do the following 6 funtions
- take in nutrients and water
- exchange gases
- remove waste
- obtain energy
- reproduce
- grow
specialised cells
cells that have a specific function and have unique structural adaptations eg: muscle cell
Tissues
groups of similar specialised cells that work together to carry out a function eg: muscle tissue
Organs
two or more tissues that group together to perform a task they have distinct structure eg: heart
Systems
organs that work together to form an organ system eg: circulating nutrients
vascular plant
have their own circulatory system called the vascular system
purpose of the vascular system
- gather water
- transport gases
- transport nutrients
root hair cells
roots of plants that absorb water from the soil, they have a branched structure to increase their SA hence increasing absorption efficiency
stomata
tiny pores in plant tissue through which gas exchange occurs. It allows water vapour and oxygen out and carbon dioxide into the leaf.
guard cells
specialised cells that surround the stomata they open and close the stomata pores depending on the gas exchange and water needs of the plant
two types of vascular plant tissue
- xylem
2. phloem
Xylem
movement of water from the roots to the rest of the plant through a process called transpiration
transpiration
passive movement of water
- heat energy causes evaporation of water in the leaves through the stomata
- the internal pressure of the xylem vessels is reduced (low pressure) which generates a pulling force
- it pulls water up from the roots against the force of gravity to replace the lost water
purpose of transpiration
- absorb necessary water
- transport minerals
- cool down
Phloem
transports organic solutes from (source) leaves to (sink) roots and other tissues; enables molecules to travel in more than one direction such as; sugar through a process called translocation
structure of the phloem
cells in the phloem tissue form rows called sieve tubes
their wall is perforated this forms sieve plates
translocation
active process of moving sugars from leaves to other tissues in the plant. Sucrose is pumped into companion cells which move into the sieve tube cells.
leaf is the site of what
gas exchange
when guard cells are turgid what are the pores
open
when guard cells are flaccid what are the pores
closed
what pressure is generated from the loss of water from the leaves
a negative presure which creates a pulling force pulling up more water to replaced the lost
name the two paths water molecules can travel
symplastic/cytoplasmic pathway-through the cells
apoplastic/extracellular pathway-via cell walls
name 4 stimulants for an affect on transpiration rate
light=increased rate
temp=increased rate
wind=increased rate
humidity=decreased rate
xerophytes
live in environments with a shortage of water
- shortage of leaves
- low growth
define homeostasis
maintenance of a stable internal environment (fluid surrounding the cell) despite changes to the external environment (rest of the body)