CHAPTER 4COMMON REQUIREMENTS OF LIVING THINGS: SINGLE CELLS AND PLANTS

• AUTOTROPHS – living things that are able to produce their own food through photosynthesis or chemosynthesis.

• HETEROTROPH – an organism that relies on other living things for its energy and nutrients. Heterotrophs are unable to produce their own food.

• SINGLE CELLED ORGANISMS- a single celled organism has a high surface area to volume ratio, because of this diffusion is sufficient for them to obtain all their requirements and to remove wastes.

PLANTS AND THEIR REQUIREMENTS

• Land/terrestrial plants require a constant supply of nutrients, water, CO2, sunlight. All are needed for growth & survival.

• Plants are found in many different locations and survive/thrive so they must be well adapted to the environment they are found in.

• Plants fall into 2 groups, those that produce seeds(enclosed for protection)

&flowers(angiosperms) and those that don’t produce enclosed seeds(gymnosperms) – such as ferns/mosses/pines.

• Angiosperms = enclosed ovule or seeds(in the fruits and flowers). These developed

from the gymnosperms many millions of yrs ago. • Gymnosperms = naked ovules or seeds(in the form of cones or spores etc on the

back of leaves) •

PLANTS

• Green plants are autotrophs and can produce their nutritional requirements from carbon dioxide, water and inorganic nutrients.

• Soil provides plants with mineral salts (such as calcium, phosphorus, potassium, sulfur and magnesium) which are the products of weathering of rocks.

• These nutrients are dissolved in a thin film of water that covers soil crumbs and they are taken up as ions by the root hairs using active transport.

NITROGEN

• Plants also require nitrogen. Atmospheric nitrogen is unusable and the plants mainly rely on nitrifying bacteria to perform Nitrogen fixing (the process of converting atmospheric nitrogen into nitrates suitable for plant use).

• Carnivorous plants obtain nitrogen from the tissue of other living organisms usually insects.

PITCHER PLANT

PLANT TRANSPORT SYSTEMS

• Plants need to transport several substances• Water: from the roots to the leaves for photosynthesis.•

• http://www.youtube.com/watch?v=C1_uez5WX1o• http://www.youtube.com/watch?v=g78utcLQrJ4• http://www.youtube.com/watch?v=pE82qtKSSH4

• Sugars: made in the leaves and transported to the other areas of the plant.

• Inorganic nutrients: obtained from the soil, dissolved in water and transported by the xylem.

• These materials are transported by vascular tissue, xylem and phloem.

• Photosynthesis worksheet.

VASCULAR BUNDLES:XYLEM AND PHLOEM

• Vascular means “vein” and these bundles are the veins of the plant. They are made up 2 types of cells; Xylem and Phloem.

• Xylem tissue carries water and dissolved minerals from the roots of the plant to the leaves.

• Phloem tissue carries glucose from the leaves to the rest of the plant.

XYLEM• Xylem is mostly made up of vessels with

thickened (lignified) walls providing strength and support to the plant.

•

• At the roots water is taken up by osmosis.

• In the stem water moves upwards by capillary action. Water molecules are attracted to each other and to the walls of the xylem creating a continuous stream of water.

• In the leaves water movement is caused by transpiration

pull; the ongoing loss of water through the leaves decreases the water concentration in that area and creates a concentration gradient facilitating the movement of water upwards.

PHLOEM• Phloem transports the organic products of photosynthesis

(sugars) from the leaves to the rest of the plant. It contains sieve tubes which lack nuclei. Phloem also includes companion cells which have a nuclei and organelles. Companion cells control the activity of the sieve tubes and keeps them alive.

• Sugars are transported by the process of translocation. They are actively loaded at the source of sugar manufacture in the leaves and transported to areas referred to as sinks (sites where the sugar is either used up or stored until required).

http://www.pearsoned.ca/school/science11/biology11/sugartransport.html

• http://www.youtube.com/watch?v=r-z7hbCFI2o

• http://www.pearsoned.ca/school/science11/biology11/sugartransport.html

• Discuss answers to questions – 1, 2, 5, 7, 8, 9, 10, 11 and 12

TRANSPORT PROCESSES

• Transpiration: this is a form of passive transport where water vapor is lost through the stomata in the leaves of plants.

• Translocation: is the active transport of sugars from the leaves through phloem to other parts of the plant.

• http://www.youtube.com/watch?v=AVLQl-iEZqA

• Worksheets on transpiration and translocation.

• BRING OUT LEAF MODEL.

• http://www.youtube.com/watch?v=co0JdqUlycg

LEAF STRUCTURE AND ADAPTATIONS• Photosynthesis occurs in the leaves of plants. They have a

number of adaptations which allow for photosynthesis to occur efficiently.

• Surface area: Volume ratio• Leaves are thin and flat enabling maximum exposure to

sunlight.• Cuticle• This is a waxy surface found on the upper epidermis. It has 2

functions – to protect the leaf and to limit water loss by keeping water inside the leaf

• Epidermis• The upper and lower sections of the leaf are called the

epidermis (skin). Sunlight is able to pass through these layers to reach the food making cells inside the leaf.

• Air spaces• These are gaps between mesophyll cells that let gases

and water vapour move around the cells.• Stomata• The surface of the leaf has a lot of tiny holes (or pores)

called stomata (if there is only 1 it is called a stoma). Stomata are usually located on the underneath side of the leaf .

• Stomata are surrounded by guard cells. A stoma opens when guard cells absorb water and close when they lose water. As a result, stomata tend to be open when a plant is experiencing moist conditions and closed in dry conditions.

Mesophyll cells

• There are 2 types of mesophyll cells and they both contain many chloroplasts. Chloroplasts contain the green pigment, chlorophyll which allows photosynthesis to occur.

• Palisade Mesophyll are the long thin cells located just under the upper epidermis and spongy mesophyll are the irregular shaped cells found in the centre of the leaf.

LEAF STRUCTURE (show model )

Hand out diagram to label and paste into notes Typical leaf

• Worksheet on Leaf structure

PLANTS REMOVING WASTES

• Apart from removing unwanted gases, deciduous plants can store wastes in leaves, which then drop off in Autumn.

• Non-deciduous trees, such as gum trees, transfer unwanted material via the phloem to the bark before it is shed.

• Woody plants store some wastes in non-living tissue.

• Certain plants remove wastes by excreting them in resins, waxes and complex chemicals like latex from rubber trees.

• Worksheet on excretion in plants

• Discuss answers to questions 14, 16, 17, 18, 20, 22, 23, 24, 25 and 26