module 2: organisation of living things

Question 1

types of cells

Answer 1

• unicellular
• colonial
• multicellular

Question 2

colonial cells

Answer 2

• group of cells or organism working collectively is called a colony
• may be uni or multicellular
• can exist independently , except in multicellular organism colonial organisms cannot exist alone
• each cell or member of the colony function individually

Question 3

formation of specialised cells

Answer 3

• when cells become specialised they differentiate - develop structures enabling them to carry out their function
• originate from stem cells (undifferentiated cells with the ability to divide repeatedly, embryonic or adult stem cells)
• specialised cells cannot survive independently - rely on other cells to carry out functions they cannot

Question 4

autotrophs

Answer 4

• produce their own organic compounds and energy from inorganic compounds from their environments, e.g. carbon dioxide and inorganic materials such as nitrates
• can be divided into two groups
  
  • photoautotrophs - use light energy
  • chemoautotrophs - use chemical energy

Question 5

hetertrophs

Answer 5

• rely on consuming other organisms
• must have a supply of organic molecules
• obtain nutrients from their living environment
• consumers and decomposers in the food chain or web
• require systems that help them break down and absorb nutrients they obtain by ingesting other living things
• include all animals and fungi

Question 6

vascular plants

Answer 6

• contain the organs: leaves, stem, roots, flowers seeds
• contain the systems: root, shoot, vascular system

Question 7

non-vascular plants

Answer 7

• plants without a vascular system consisting of xylem and phloem
• possess simpler tissues that have specialised functions for the internal transport of water
• need a constant supply of water to live and reproduce, do not have vein-like structures
• absorb water and nutrients through the surface of their leaves
• reproduce by spores in capsules (wild-dispersal)
• nutrients absorbed and waste removed by diffusion and osmosis

Question 8

vascular system

Answer 8

• responsible for the transport and distribution of organic compounds, water, minerals and gases around the plant
• two types of tissue
  
  • xylem
  • phloem

Question 9

xylem

Answer 9

• carry water and water-soluble nutrients and minerals from the soil via the roots
• consists of two main types of elements - xylem tracheids and xylem vessels, with other cells such as parenchyma and fibres in between
• movement upwards
• walls of xylem vessels and tracheids are reinforced with lignin thickening laid down in rings, spirals or other regular patterns, preventing the vessels from collapsing, help the easy movement of water and dissolved substances
• movement of water up the xylem occurs mainly as a result of a transpiration steam that develops: as water evaporates through the stomata of leaves, it sets up a concentration gradient across the leaf, creating a suction pull on the water and dissolved minerals in the xylem tissue

Question 10

phloem

Answer 10

• composed of thin-walled cells that transport sugars (dissolved sucrose) and other plants products from one part of the plant to another
• two types of phloem cells: sieve tube cells and companion cells
  
  • sieve tube cells are long, thin cells that have large pores and perforated cell walls called sieve plates, they do contain mitochondria and ER but no other organelle. sieve tube cells are connected end to end and share cytoplasm to form a channel so sugar and other products can flow
  • companion cells are found alongside sieve tubes and contain a nucleus and other organelles that sieve tube lacks, they assist the effectiveness of sieve tubes as they provide ATP and nutrients and assist the loading and unloading of sugars into the sieve tube

Question 11

root system

Answer 11

• function is to anchor the plant and absorb water and inorganic materials from the soil
• large surface area
• epidermal cells in the roots are responsible for absorption of water through osmosis and inorganic nutrients from the soil through diffusion
• water moves across the root tissues from outer epidermal layer to vascular stele in the centre of the root and into the xylem tissue
• have not chloroplasts, no photosynthesis, carry out aerobic respiration

Question 12

shoot system (stem)

Answer 12

• provides structural support and a transport pathway
• consists of 3 main functions
  
  • dermal - outer layer provides protection, waterproofing and control of gas exchange
  • vascular - composed of the xylem and phloem within vascular bundles
  • ground tissue - fills in around vascular tissue

Question 13

shoot system (leaves)

Answer 13

• responsible for 3 important processes in plants
  
  • photosynthesis: absorb sunlight and carbon dioxide during the day, release oxygen, provide chlorophyll to make and transport glucose
  • transpiration: release water to cool the plant, suction pull to lift water from the roots to the top of the plant
  • exchange of gases: release of excess oxygen from and carbon dioxide
• leaves are arranged to expose them to the max amount of sunlight possible, angled so that the sunlight strikes the upper surface of the leaves
• large SA allows max absorption
• transparent epidermis allows sunlight to penetrate the photosynthetic cells beneath

Question 14

outermost layer: epidermis

Answer 14

• forms a single protective layer of cells on the upper and lower surfaces of the leaf, transparent
• secretes a waterproof cuticle which prevents evaporation of water
• contains guard cells that occur in pairs around the stoma (stomata) and these control exchange of gases and loss of water from leaves

Question 15

middle layer: mesophyll

Answer 15

• cells in the centre of the leaf consist of two types:
  
  • palisade mesophyll: found most commonly in one or two rows below the upper epidermis, regularly arranged, elongated cells packed with green chloroplasts, it is in these cells that most of the plant’s photosynthesis occurs
• spongy mesophyll: usually situated between the palisade cells and the lower epidermis, contain fewer chloroplasts and are irregularly arranged with large spaces between, this arrangement enables gases and water vapour to move easily between the cells and stomata

Question 16

gas exchange

Answer 16

• 3 requirements for efficient gas exchange:
  
  • large surface area
  • moist gas exchange membrane: gass must dissolve in water before diffusing
  • close contact between the gas exchange membrane and the blood supply: diffusion is only efficient over a short range
  • greater concentration of required gas on one side of the membrane
• gas exchange occurs across the thin walls of alveoli

Question 17

alveoli

Answer 17

• tiny sac in our lungs
• there are millions in each each lung and they have moist, thin walls
• they massively increase the surface area inside our lungs
• they have a lot of tiny blood vessels called capillaries

Question 18

mammals

Answer 18

• the nasal cavity is a large, air-filled space behind the nose responsible for warming, moisturising and filtering the air using hair and mucus, the pharynx is a passageway leading from the nasal cavity to the esophagus and larynx
• epiglottis is a flap above the trachea that prevents the food from entering the windpipe
• larynx is involved in breathing, producing sound and protecting the tracheae from food aspiration, trachea is a tubular structure responsible for transporting air
• the trachea splits into two structures called bronchi leading into each lung, bronchi then branch of into bronchioles that deliver air to tiny sacs called alveoli
• alveoli are the gas exchange surface, capillaries are blood vessels that surround the alveoli so that O2 can enter and CO2 can leave, when oxygen binds with a red blood cell it is called oxyhemoglobin
• the diaphragm is a muscle below the lungs that contracts and expands causing the lungs to inhale and exhale

Question 19

fish

Answer 19

• much more efficient respiratory systems since they need to extract max amount of oxygen from water and diffusion is slower in liquid than air
• gills are the respiratory organ for fish, protected by an operculum or gill cover, fish keep a constant flow of water moving across the gill filaments for efficient gas exchange
• flow of capillaries is in the opposite direction to the flow of water to create a concentration gradient, called a counter current and causes 95% of oxygen to be obtained from the water passing over the gills

Question 20

insects

Answer 20

• respiratory system is called a tracheal system and consists of holes called spiracles that form a row along both sides of their body, the spiracles are connected to tubes called tracheae
• tracheae lead into smaller tubes called tracheoles which reach to the surface of most cells of the body where gas is exchanged

Question 21

types of digestion

Answer 21

• chemical digestion:
  
  • involves enzymes
  • enzymes break down complex chemical compounds into simpler smaller molecules so they can be absorbed into the blood
• physical digestion
  
  • cutting and mashing of the food that occurs by chewing
  • break the food down into smaller parts to increase SA:V ratio so it can be attacked by enzymes

Question 22

digestive system

Answer 22

three kinds of digestive enzymes:
- amylase - act on carbohydrates
- protease - act on protein
- lipases - act on lipids

Question 23

distribution of vascular tissue in flowering plants

Answer 23

• in roots, xylem is found in the centre of the roots, usually in a star or cross shape with phloem tissue between the arms of the xylem
• in the stem, the xylem and phloem tissue divides into vascular bundles
• bundles of vessels of xylem and phloem continue from the stem up leaf stalks, forming the veins in leaves

Question 24

cohesion and adhesion

Answer 24

cohesion - water molecules bond to each other
adhesion - water molecules bind to the walls of xylem tubes

Question 25

stomates (stomata)

Answer 25

• tiny openings or pores that enable gaseous exchanges
• usually found in plant leaves, can also be found in some stemms
• regulate gas exchange between the plant and environment and control water loss by changing the size of stomatal pore