bio unit 1 exam revision

Tissue

A group of cells of one type that perform a particular function at one time

Organ

Different tissues that work together to perform a particular function

System

A group of organs that work together to perform a major function for the organisms survival

What are vascular plants

Plants that have a network/system of conducting elements to move materials around the plant to every cell

What part of the tree is the xylem known as

The wood

What part of the tree is the phloem known as

The bark (living tissue)

What does the xylem carry within the plant

Water and dissolved materials - movement is a one way system from roots to shoots

Two types of cells in the xylem

Tracheids and xylem vessels - dead cells that form hollow tube, strengthened by lignin (polymer)

What does the phloem carry around the plant

Organic material in the form of sucrose - Both up and down the plant (multi-directional)

Two types of cells in phloem

Sieve tubes and companion cells - living cells arranged in long tubes with cytoplasm connecting one cell to the next

Root system in xylem vessels

Functions: uptake of water

Root hairs: Increased surface area, water absorbed up to 130 times greater than surface area of shoot system

Entry of water and minerals: 'Force' of water entering root hairs/roots (via osmosis) and dissolved substances (diffusion and active transport) - creates root pressure, forces water up stem

Shoot system in xylem vessels

Vascular plants able to grow tall as they have the capacity to move water and mineral nutrients to a great height

Adhesion

Water sticks to other molecules (leaf)

Cohesion

Water molecules stick to itself (forms water droplet)

Surface tension

Water has high levels of surface tension due to high cohesion of molecules in the surface layer creating a minimal surface area

Capillarity

Change in surface tension

Narrowness of the tube affects adhesive forces

Narrow tubes increase the further the molecules reach either side (increased surface tension)

Cohesion, adhesion, and surface tension assist in capillarity

Transpiration

The evaporation of water

Transpiration stream

Continuous movement of water up the plant (from roots to leaves) in xylem vessels due to the evaporation from the leaves, pulling the next molecule up

Stomata

Small openings (pores) in the epidermis of the leaf

Surrounded by guard cells (containing chloroplasts), can open and close - closed at night because no water pressure from osmosis

Factors affecting rate of transpiration

Temperature

Air movement

Humidity

Temperature affecting rate of transpiration

Increased temp increases energy of water molecules which will increase evaporation from stomata (transpiration)(heat of the sun)

Air movement affecting rate of transpiration

Increased air movement (wind), moves evaporated water molecules away from leaf - more H2O can evaporate (transpiration)

Humidity affecting rate of transpiration

Amount of moisture in the air

Increased humidity means less space outside stomata for the water to move into - decreased evaporation (decreased transpiration)

Translocation in phloem

Movement in the phloem that transports sucrose (converted from glucose in photosynthesis) to every cell of the plant from a site of synthesis (leaves) to a site of use or storage as starch (roots)

Two way movement - Day - downwards, night - upwards

What does it mean by translocation being an active process

Translocation requires energy supplied by nearby companion cells (many mitochondria)

Energy originates from sunlight energy

Excretory system

Removes waste from the body

Cell reactions create waste products - metabolic waste

Organs of excretion

skin - sweat contains low levels of salt and lower levels of nitrogenous waste

Lungs - Removes carbon dioxide

Kidneys - Role in excretion of nitrogenous waste as well as water balance

Liver - Red blood cells have limits lifespan. As they die they produce waste broken down by liver and used in production of bile

Forms of nitrogenous waste produced in metabolism of proteins

Ammonia, uric acid, urea

The form excreted depends on the availability of water in the environment

Ammonia

Toxicity - high

Water needed - high

Animals - fish (aquatic)

Uric acid

Toxicity - low

Water needed - low

Animals - birds, reptiles

Urea

Toxicity - less toxic (moderate)

Water needed - some

Animals - humans, mammals

Mammalian excretory/urinary system

Two key roles of the kidneys in humans

Filter metabolic wastes (urea) and excrete excess hormones and vitamins

Help maintain (blood solution stable) water and ion balance in the blood by excreting those in excess

Structure of kidney

Renal pelvis

Central area where urine collects and exits via the ureter

Cortex

Outermost layer, filtration area

Medulla

Inner section, stiated (striped), where balancing of the blood composition occurs

Nephron

Functional unit of the kidney which filters the blood

About one million in each kidney

Nephron structure

Branch of renal artery, bowman's capsule, glomerulus, renal capillaries, branch of renal vein (out), proximal tubule, loop of henle, distal tubule, collecting duct, goes to ureter

3 main process of nephron functioning

Filtration, reabsorption, excretion

Filtration

Bowman's capsule

Blood enters glomerulus under high pressure

Substances are forced through little spaces in capillary walls, into bowman's capsule

Filtrate contains: most water, nitrogenous wastes, nutrients, salts

Proteins and blood cells are too large

Reabsorption

Proximal tubule, loop of henle, distil tubule

Molecules in filtrate needing to be put back into bloodstream (passive or active)

Actively reabsorbed - sodium, nutrients

Passively reabsorbed - Water and chloride ions

Reabsorbs what the cell needs - any excess or nitrogenous wastes continue towards ureters

Excretion

Collection duct

Removal of waste and excess material

As filtrate travels down collecting duct, more water is reabsorbed

Fluid that reaches end of tubul contains N waste, excess water, excess salts - urine - hypertonic

Pressure builds in bladder, sphincter at base opens called micronutrition

Regulation of water balance in vascular plants

Stomata - during the day, guard cells become turgid from water pressure from osmosis, causing them to bend and open (hypotonic)

Typically at night, they close when there is less water pressure, causing guard cells to become flaccid (to reduce water loss, sometimes with dry soil and low water uptake)

External environment

The area outside the tissue (cellular) area that is in continuous with outside the organism

(respiratory system, digestive system, inside tubules in excretory system)

Internal environment

Fluid within the body (tissue/cellular area)

Extracellular fluid

Surrounding the body cells - interstitial fluid and blood plasma

Intracellular fluid

Inside the cells - cytosol

Optimum range

Range in which humans thrive and function at their best

Tolerance range

Humans can survive and not thrive

Physiological stress

Where the mechanisms to deal with fluctuations break down, and if the situation doesn't change, the organism will malfunction and die

Stimulus response model

How the cells and organ systems of the human body detect and respond to changes in external and internal environment

Stimulus

Input

The change in the internal or external environment

Receptors

Detects stimulus

Specialized cell, specific for that stimulus

Communication

Transmission of messages (usually nervous system or hormones)

Control centre

Effector

Body tissue or organ that carries out a response

Response

Output

Appropriate action that occurs

Chemoreceptors

Detects chemicals - smell, oxygen and ion levels, blood glucose concentration, blood water concentration