B 4 Summary Plant Cells Vacuole Cell Membrane

B 4 Summary

Plant Cells Vacuole Cell Membrane Contains cell sap Allows substances in/out of cell Cell Wall Provides support Chloroplast Where photosynthesis takes place Nucleus Cytoplasm Controls the cells activities Where all cell reactions take place

Leaf structure Palisade layer Spongy layer Stomata (can’t see on my diagram) Cuticle Upper epidermis Chloroplasts Vacuole Cytoplasm Air spaces Phloem Xylem Lower epidermis Guard cells

Keywords - Definitions • Cuticle – waxy layer on the top of a leaf. This helps to stop water from evaporating. A cactus has a thick cuticle. • Palisade layer – Closely packed together, elongated and contains lots of chloroplasts for photosynthesis. • Xylem – The vessel that carries water • Phloem – The vessel that carries dissolved food substances • Guard cell – Surround the stomata and cause it to open or close. • Stomata (or stoma) – Holes underneath the leaf. Needed for gas exchange for photosynthesis. HOWEBER water can evaporate from these holes. This is called TRANSPIRATION.

Leaf Adaptations • Broad so large surface area • Thin so short distance for gases to travel • Contain chlorophyll to absorb light • Have a network of veins for support and transport • Stomata for gas exchange (by diffusion)

Osmosis • Osmosis is the movement of water across a partially permeable membrane from an area of high water concentration (a dilute solution) to an area of low water concentration (a concentrated solution) • Osmosis is a type of diffusion

Osmosis Extras…… • How does water move through a plant? – Absorption from the soil through root hairs – Transport through the stem to the leaves – Evaporation from the leaves (transpiration) • What is the role of the root hairs? – They increase the surface area to increase uptake of water • How is the leaf adapted to reduce water loss? – Waxy cuticle – Small number of stomata on the upper surface

Key Terms • Flaccid – when water leaves the plant cells and the cell becomes soft and floppy • Plasmolysed – when water leaves a cell and the contents shrink and there is less water pressure against the cell wall • Turgid – when water enters a cell and it swells up. The cell becomes hard and rigid. (turgor pressure against cell wall)

Transpiration • Transpiration is the evaporation and diffusion of water from inside the leaves

Leaf, Stem, Root

Absorption by the Roots

Xylem and Phloem • Xylem (TRANSPIRATION) – Movement of water and minerals from the roots to the shoot and leaves • Phloem (TRANSLOCATION) – Movement of food substances (sugars) up and down stems to growing and storage tissues

Affects on Transpiration • Light Intensity increases – stomata open, more water escapes • Temperature increases – random movement of water molecules increases, more water escapes • Wind – more water molecules near stomata to be removed, increases evaporation and diffusion of water • Dry Conditions – low concentration of water outside leaf, more diffusion of water from inside to outside

Plant Minerals Mineral Used for: Symptoms if Deficient Diagram Nitrates Phosphates Potassium Magnesium To make DNA & cell amino acids membranes, and proteins respiration for growth & growth To help enzymes in respiration & To make chlorophyll for Poor growth and yellow leaves Poor root growth and discoloured leaves photosynthesis Poor flower & fruit growth and discoloured leaves photosynthesis Yellow leaves

Active Transport • Minerals exist in the soil in quite low concentrations • Plants need to use energy (from respiration) to take them into the roots • They move against the concentration gradient

Biomass Pyramids • Biomass – the mass of living material • This goes down as you move along the food chain • Can draw as a pyramid – always look right way up! Grade C

Energy Transfer • Plants use a small percentage of the sun’s energy to make food during photosynthesis • This energy then moves through the food chain through feeding • Energy is lost at each stage – through heat and waste (egestion) • So much energy is lost at each stage there is not enough to support more organisms after 4 -5 stages Grade C

Interpreting Data Can you work out the 2 nd and 3 rd trophic levels? Rosebush Greenfly Ladybird Bird 80, 000 KJ 10, 000 KJ 900 KJ 40 KJ • The numbers show the amount of energy available to the next level e. g. 80, 000 KJ is the energy available to the greenfly • You can work out how much energy is lost at each trophic level • e. g. energy lost at 1 st trophic level is 80, 00010, 000 = 70, 000 KJ

Energy Efficiency Can you work out the 2 nd and 3 rd trophic level efficiency? Rosebush Greenfly Ladybird Bird 80, 000 KJ 10, 000 KJ 900 KJ 40 KJ • You can also calculate the efficiency of energy transfer: Efficiency = energy available to the next level x 100 energy that was available to previous level E. G. 1 st trophic level efficiency = 10, 000/80, 000 x 100 = 12. 5% efficient

Biomass and Biofuels • The mass of plants and animals is called biomass • Biomass can be eaten, fed to livestock, used as a source of seeds, used as a biofuel • Wood, alcohol (fermenting) and biogas are all examples of biofuels

Intensive Farming • This means trying to produce as much food as possible from the land, plants and animals available • Pesticides can be used to kill pests e. g. insecticides to kill insects and fungicides to kill fungi • Herbicides can be used to kill plants (weeds)

Pesticide Build-Up • Pesticides may enter and accumulate in food chains • Pesticides may harm organisms which are not pests e. g. bees • Concentration of DDT in parts per million (ppm) in a food chain: Lake Microscopic life Fish Grebes (birds) (0. 02) (5) (2000) (get a lethal dose)

Food Production • The efficiency of food production can also be improved by: – Restricting energy loss from food animals by • limiting their movement • Controlling the temperature of their surroundings – Using hormones to regulate the ripening of food on the plant and during transport to consumers

Intensive Farming • It is very efficient • More energy is usefully transferred because: – There are fewer weeds in crops – There are fewer pests to attack and eat crops or cause disease in livestock – Less heat is lost from animals kept in sheds and their movement is restricted

Hydroponics • Can be used to grow lettuces or tomatoes • Allows plant growth in areas of barren soil • Does not use soil so less chance of disease or pests • Roots are specially treated in water that contains required amounts of fertiliser and oxygen

Organic Farming • A farmer who does not use manufactured chemicals is called an organic farmer e. g. – Artificial fertilisers – Herbicides – Pesticides

Organic Farming • Biological control e. g. introducing pests like ladybirds or wasps • Use of animal manure and compost • Crop rotation • Use of nitrogen fixing crops e. g. peas and beans • Weeding • Varying seed planting times

Advantages and Disadvantages • Expensive chemicals do not have to be bought • There is no chemical pollution or build up in food chains • Biological control methods are often slow and do not kill all the pests • Crop yields are reduced and the cost of production is higher • Some people think the products taste better

Decay • Earthworms, maggots and woodlice all feed on dead and decaying matter – they are called detritivores (they produce a large SA for saprophytes) • Bacteria and fungi are saprophytes – they release enzymes to break down the dead matter

Conditions for Decay • Microorganisms, temperature (warmth), oxygen (good aeration e. g. regular mixing of contents) and moisture all needed for decay • Microorganisms are used to: – Break down human waste (sewage) – Break down plant waste (compost)

Food Preservation • Preserving food stops it from decaying: – Adding sugar or salt – Canning – Cooking – Freezing – Drying – Adding vinegar

The Carbon Cycle • Carbon dioxide is removed from the environment by green plants for photosynthesis • The carbon is used to make carbohydrates, proteins and fats which make up the body of plants • Some carbon is returned to the atmosphere when plants respire

The Carbon Cycle - 2 • Green plants are eaten by animals and so on – the carbon becomes part of their bodies • Animals respire and return some carbon to the atmosphere • When plants and animals die, micro-organisms feed on their bodies • Carbon is released to the atmosphere when they respire

Carbon Cycle at Sea • Marine organisms make shells made of carbonates • Shells become limestone • Carbon returns to the air as carbon dioxide during volcanic eruption or weathering

The Nitrogen Cycle – B 4 • 78% of the air is Nitrogen – it is very abundant • BUT it is too un-reactive to be used directly by animals and plants • Nitrogen is an important element that is used to make proteins. • It is constantly recycled in the Nitrogen Cycle

The Nitrogen Cycle (Grade C) – B 4 • Plants take in nitrates from the soil to make protein for growth • Feeding passes nitrogen compounds along a food chain or web • Nitrogen compounds in dead plants and animals are broken down by decomposers into nitrates and returned to the soil

The Nitrogen Cycle (Grade A) – B 4 • Soil bacteria and fungi, acting as decomposers, convert proteins and urea into ammonia • This ammonia is converted to nitrates by nitrifying bacteria • Nitrates are converted to nitrogen gas by denitrifying bacteria • Nitrogen gas is fixed by nitrogen-fixing bacteria living in root nodules or the soil or by the action of lightening

Nitrogen Cycle - B 6 Nitrogen recycling depends on different types of bacteria: • Saprophytic soil bacteria start to decompose the dead animals and plants forming ammonia • Nitrifying bacteria, such as Nitrosomonas and Nitrobacter, use the process of nitrification to convert ammonia into soluble nitrates that plants can absorb • Nitrogen-fixing bacteria such as Azotobacter, Clostridium in the soil and Rhizobium in the root nodules of leguminous plants, convert nitrogen from the air and use it to make their own proteins

Saprophytes