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)
tolerance range
greater the ability to regulate
stages of homeostasis
stage 1: detection of change from a stable state by receptors
stage 2: receptors stimulate a response to this change by effectors
the loss of water vapour is called what
transpiration
how do plants minimise water loss
by using guard cells to open and close the stomata
stomata tend to be open and closed when
open during the day and closed during the night
3 forces that water is under in the xylem tubes
a pulling force exerted by transpiration in the leaves
a pushing force exerted by osmosis
adhesion and cohesion forces of water molecules (unbroken stream called transpiration stream)
xylem cells are what
dead cells-no cellular components
compared to atmospheric pressure the xylem vessels are what
much lower-they can withstand low pressures due to their thick vessels
water molecules are cohesive between each other due to what
hydrogen bonding
water molecules are adhesive to the hydrophilic cellulose fibres in the xylem walls due to what
hydrogen bonding
how does water move between cells
osmosis from high water concentration to low water concentration
what is the only energy required for the transpiration pull process
heat energy that causes the evaporation of water from the leaves
where does translocation transport first occur
areas of new growth
adhesion
Adhesion is the force of attraction between two particles of different substances (e.g. water molecule and xylem wall)
cohesion
force of attraction between two particles of the same substance (e.g. between two water molecules)
vascular bundle
the grouping of xylem and phloem vessels in a plant
Chemical digestion
break down of food molecules by digestive enzymes
negative feedback loops
Negative feedback are mechanisms that counteract the stimulus to bring a condition back to normal (restores original state).
Negative feedback loop caused by drop in glucose levels
Chemoreceptors in the pancreas detect change and release glucagon from the pancreas which causes the breakdown of glycogen to glucose in the liver, increasing glucose levels back to normal
what are hormones responsible for
the communication between tissues and organs
positive feedback
A type of regulation that responds to a stimulus by initiating responses that will increase the stimulus.
eg: release of oxytocin during childbirth to stimulate contractions
What is faster? The hormonal or the nervous system?
The hormonal system is slower than the nervous system because the molecules have to be passed through the blood or tissue to reach the target cells, where as nerve action occurs due to electrical impulses
what lasts longer? The hormonal or the nervous system
Hormonal system action is more sustained than the nervous system because hormones must be metabolised before inactivation occurs.
Chemoreceptors
Stimulated by chemical changes eg: taste, smell, blood ph
Mechanorecpetors
stimulated by forces or pressure e.g. sound, touch, vibration
Photoreceptors
Stimulated by light. Located in the retina of the eyes
Thermoreceptors
Stimulated by temperature changes. Located in the skin and brain and are involved in temperature regulation.
The basic structure of a vascular plant contains
Leaves (photosynthesis)
Root (to absorb water)
Stem (stability)
feedback loop
A stimulus-change to a stable state which causes a signal
A receptor-detects the signal from the stimulus
A control centre-is where the signal is transferred to (hypothalamus)
An effector-is where the signal is sent to
A Response-is what the effector works to perform
what are phloem sieve tubes controlled by
companion cells
what does the hormone insulin do
stimulates cells to absorb glucose from the blood
when do stomata tend to close
when it is hot and dry to prevent excess water loss
where are stomata found
in the epidermis of leaves and some stems
what are the two most important systems in maintaining homeostasis in animals
endocrine system and the nervous system
insulincoh negative feedback loop
If glucose levels get too high, the body releases insulin into the bloodstream. Insulin causes the body’s cells to take in and store glucose, lowering the blood glucose concentration. If blood glucose gets too low, the body reduces the release of insluin and releases glucagon, which causes the release of glucose from some of the body’s cells.
type 1 diabetes
body does not produce sufficient insulin hence glucose is not removed from the blood stream
hypoglycaemia
blood glucose levels are too low (too much insulin)
hyperthyroidism
production of too much thyroxine hormone
type 2 diabetes
it is caused by an ineffective homeostatic repsonse to insulin
marram grass
roll their leaves to reduce water loss
