AQA Additional Science

AQA Additional Science
21/11/2018 AQA Additional Science Biology Unit 2 W Richards The Weald School

B2.1 Cells and Cell Transport
21/11/2018 B2.1 Cells and Cell Transport

A Typical Animal Cell 4) Ribosomes – protein synthesis happens here 1)
21/11/2018 4) Ribosomes – protein synthesis happens here 1) Cytoplasm - this is where the reactions happen and these are controlled by enzymes 2) Nucleus – controls the cell’s activities 5) Mitochondria - energy is released here during respiration 3) Cell Membrane – controls what comes in and out

A Typical Plant Cell: 21/11/2018 Cell wall – made of cellulose which strengthens the cell Cell membrane – controls what comes in and out Chloroplasts (containing chlorophyll) – this is needed for photosynthesis Nucleus – controls what the cell does and stores information Large vacuole – contains sap and helps support the cell Cytoplasm – Chemical reactions happen here

Bacteria and Yeast 21/11/2018 Bacteria and yeast are two examples of single-celled organisms: Bacteria – containing cytoplasm and a membrane surrounded by a cell wall. The genes are NOT in a distinct nucleus. Yeast – contain the usual cytoplasm, nucleus and membrane surrounded by a cell wall.

More specialised animal cells
21/11/2018 I.D: Function: Features: Red Blood Cell Carries oxygen around the body No nucleus and large surface area White blood cell Egg cell (ovum) Ciliated epithelial cell Nerve cell (neurone)

Oxygen passes into cells by diffusion
21/11/2018 Diffusion is when something travels from an area of high concentration to an area of low concentration. For example, consider the scent from a hamburger… The “scent particles” from this hamburger are in high concentration here: Eventually they will “diffuse” out into this area of low concentration: Oxygen passes into cells by diffusion

Words – faster, low, gradient, temperature, energy
Diffusion Summary 21/11/2018 Diffusion is when particles spread from an area of high concentration to an area of ___ concentration. The particles move along a “concentration _____” and this process takes no _____ (it’s a “passive” process”). Diffusion can be accelerated by increasing the _______ of the particles, which makes them move _______. Words – faster, low, gradient, temperature, energy

B2.2 Tissues, Organs and Organs
21/11/2018 B2.2 Tissues, Organs and Organs

Cell specialisation 21/11/2018 During the development of a multi-celled organism cells differentiate to form specialised cells: White blood cell Egg cell (ovum) Ciliated epithelial cell Nerve cell (neurone)

Cells, tissues, organs and systems
21/11/2018 Basically, all living things are made up of cells… A group of CELLS makes up a TISSUE A group of TISSUES makes up an ORGAN A group of ORGANS makes up a SYSTEM A group of SYSTEMS make up an ORGANISM

Here’s another example in humans:
21/11/2018 Here’s another example in humans: Muscle cells Muscle tissue Organ System Organism

An example organ: The Stomach
21/11/2018 Consider one of the body’s most important organs – the stomach: The stomach contains many different types of tissue, including: 1) Muscular tissue, to “churn up” the contents 2) Glandular tissue, to produce digestive juices 3) Epithelial tissue, to cover the outside of the stomach

An example system: The Digestive System
21/11/2018 The whole point of digestion is to break down our food so that we can get the bits we need from it. Basically, here’s how it works: 1) Glands such as the salivary gland and the pancreas produce digestive juices 2) Digestion occurs in the stomach and small intestine 3) Bile is produced by the liver and helps break down fats 4) Food is absorbed in the small intestine 5) Water is absorbed in the large intestine, leaving behind the faeces

Examples of Plant Tissue
21/11/2018 1) Epidermal tissue, which covers the plant 2) Mesophyll, where photosynthesis occurs 3) Xylem and phloem, which are used to transport substances around the plant

21/11/2018 B2.3 Photosynthesis

Photosynthesis 21/11/2018 Basically, photosynthesis is the process through which a plant makes its own food using carbon dioxide and water: That’s a nice plant. I’m going to put it in the sun and give it lots of water and air… CO2 H2O

Photosynthesis – the 4 things you need
21/11/2018 SUNLIGHT Gives the plant energy CHLOROPHYLL The green stuff where the chemical reactions happen WATER Travels up from the roots CARBON DIOXIDE Enters the leaf through small holes on the underneath

Photosynthesis equations
21/11/2018 Carbon dioxide + _____ glucose + _____ 6CO H20 C6H12O O2 Sunlight Chlorophyll The GLUCOSE produced by photosynthesis is used by the plant for _______ (through ____________). It is stored in the plant as ___________. Words – respiration, starch, water, oxygen, energy

Limiting Photosynthesis
21/11/2018 What factors could limit the rate of photosynthesis? Temperature – the best temperature is about 300C – anything above 400C will slow photosynthesis right down CO2 – if there is more carbon dioxide photosynthesis will happen quicker Light – if there is more light photosynthesis happens faster

Drawing graphs of these factors
21/11/2018 1. Temperature Photosynthesis is controlled by enzymes – these are destroyed at temperatures above 400C 2. Carbon dioxide Photosynthesis increases at first but is then limited by a lack of increase in temp or light 3. Light Photosynthesis increases at first but is then limited by a lack of increase in temp or CO2

Encouraging Photosynthesis
21/11/2018 Using knowledge of limiting factors, explain how plant growth is encouraged in a greenhouse:

What is the glucose used for?
21/11/2018 1) Glucose (sugar) can be used to make long chains of insoluble starch… Glucose molecules Starch molecule 2) Glucose can be used to make cellulose for cell walls… Glucose molecules Cellulose 3) Glucose can be combined with nitrates to make proteins (for growth)… Glucose molecules Proteins 4) Glucose can be converted into lipids (fats or oils) to store in seeds… Glucose molecules Lipid structure

2 common nutrients… Nitrates: Magnesium: Used to make proteins
21/11/2018 Nitrates: Used to make proteins Lack of it leads to stunted growth Magnesium: Used to make chlorophyll Lack of it leads to yellow leaves

B2.4 Organisms and their Environment
21/11/2018 B2.4 Organisms and their Environment

Factors affecting organisms
21/11/2018 Various factors can affect the development of organisms: Availability of carbon dioxide and oxygen Temperature Factors affecting organisms Availability of nutrients Amount of water Amount of light

Taking samples of an ecosystem
21/11/2018 Using different “sampling techniques” we can measure changes in an ecosystem. The two main measurements are: The physical conditions of a habitat (temperature etc) The populations of different species in that habitat Some common ways of measuring… Help! Measuring temp, pH etc Taking animal samples Taking samples using quadrats

21/11/2018 B2.5 Proteins

Introduction to Enzymes
21/11/2018 Enzymes are biological catalysts. They help the reactions that occur in our bodies by controlling the rate of reaction. An enzyme is basically a protein molecule made up of long chains of amino acids. These molecules are then “folded” to create a certain shape. Proteins are used in hormones, antibodies and muscle tissue. Enzyme The enzyme’s shape helps another molecule “fit” into it: Substrate This shape can be destroyed by high temperatures or the wrong pH:

Enzymes are denatured beyond 40OC
21/11/2018 Enzymes work best in certain conditions: Enzymes are denatured beyond 40OC Could be protease (found in the stomach) Could be amylase (found in the intestine) Enzyme activity Temp pH 400C Enzymes are used in industry to bring about reactions at normal temperatures and pressures that would otherwise be expensive. However, most enzymes are denatured at high temperatures and can be costly to produce.

Words – blood, lipids, proteins, digestion, starch, smaller
Enzymes in digestion 21/11/2018 Enzymes can be produced by the body to help _______. When they come into contact and react with food they break it down into ______ pieces which can then pass into the ______: Amylase (produced in the mouth, pancreas and small intestine) breaks _______ (a carbohydrate) down into glucose: Protease (produced in the stomach, pancreas and small intestine) breaks _______ down into amino acids: Bloodstream Lipase (produced in the pancreas and small intestine) breaks fats (_____) down into fatty acids and glycerol: Words – blood, lipids, proteins, digestion, starch, smaller

The digestive system 21/11/2018 The whole point of digestion is to break down our food so that we can get the bits we need from it… The main foods affected are CARBOHYDRATES – these are broken down into GLUCOSE. Hydrochloric acid is produced in the stomach to kill bacteria. Digestion also depends on “enzymes”...

Bile and The Liver 21/11/2018 Bile is a chemical produced in the liver and stored in the gall bladder. It has 2 functions: It neutralises stomach acid and produces alkaline conditions for enzymes to work in It emulsifies (“breaks down” fats: Fat globules Fat droplets

Industrial uses of enzymes
21/11/2018 Daz 1) Enzymes are used in washing powders to help digest fats and proteins in food stains. Biological washing powders will only work on 400C or lower. 2) Enzymes are used in baby foods to “pre-digest” the proteins. 3) Enzymes are used to convert starch into sugar which can then be used in food. 4) Conversion of glucose into fructose using isomerase – glucose and fructose are “isomers” (they have the same chemical formula), but fructose is sweeter.

B2.6 Aerobic and Anaerobic Respiration
21/11/2018 B2.6 Aerobic and Anaerobic Respiration

Respiration Introduction
21/11/2018 I enjoy taking samples using quadrats. In order to do this, I need energy. Where does this energy come from? Our energy comes from a process called respiration, which basically involves turning food and oxygen into energy and this reaction is controlled by enzymes.

(Aerobic) Respiration
21/11/2018 All living organisms have to move, _____, reproduce etc. Each of these life processes needs ENERGY. ___________ is the process our bodies use to produce this energy: Glucose + oxygen water + carbon dioxide + ENERGY The glucose we need comes from ______ and the oxygen from _________. Water and carbon dioxide are breathed out. The MAIN product of this equation is _________. Respiration happens in _________ in cells. Words – breathing, energy, grow, respiration, food, mitochondria

Words – nitrates, tissue, proteins, respiration, plants
Uses for this energy 21/11/2018 Animals and plants have many uses for the energy they generate from respiration: To build up sugars in ______ To build up body _______ To maintain a constant body ___________ (warm-blooded mammals only) To build up sugars, ________ and other nutrients in plants To build up amino acids and ________ Words – nitrates, tissue, proteins, respiration, plants

The Effect of Exercise Heart rate/min Breathing rate/min Rest Exercise
21/11/2018 Heart rate/min Breathing rate/min 100 225 Rest Exercise Recovery 75 175 50 125 25 75 5 mins 10 mins 15 mins 20 mins During exercise the following things happen: heart rate increases, breathing increases and arteries supplying muscles dilate. These three things all help muscles to get the oxygen and glucose they need.

Muscles and exercise 21/11/2018 When we exercise our muscles are supplied with more oxygen and glucose, increasing the rate of respiration. Muscles store glucose as glycogen which can then be converted back into glucose during exercise.

Anaerobic respiration
21/11/2018 Unlike aerobic respiration, anaerobic respiration is when energy is provided WITHOUT needing _________: Glucose lactic acid + a bit of energy This happens when the body can’t provide oxygen quick enough for __________ respiration to take place. Anaerobic respiration produces energy much _______ than aerobic respiration but only produces 1/20th as much. Lactic acid is also produced, and this can build up in muscles causing ______ and an oxygen ______. This “debt” then needs to be “repaid” by deep breathing to ________ the lactic acid. Words – debt, oxygen, fatigue, oxidise, aerobic, quicker

B2.7 Cell Division and Inheritance
21/11/2018 B2.7 Cell Division and Inheritance

X Modern Genetics Mendel’s experiment:
21/11/2018 Guten tag! My name is Gregor Mendel. I am the father of modern genetics because of the work I did on pea plants in 1865… Mendel’s experiment: X Take two plants; one which is pure-bred for tallness and one pure-bred for shortness, and cross them:

Now cross two of these plants…
Modern Genetics 21/11/2018 All the plants produced were tall. Now cross two of these plants… 3 out of every 4 plants were tall, leading Mendel to hypothesise that “for every characteristic there must be two determiners”

Modern Genetics 21/11/2018 Achtung! Unfortunately, nobody knew about chromosomes or genes when I published my findings so no one believed me until after my death, when more powerful microscopes were available.

Cells, Genes and Chromosomes
21/11/2018 Chromosomes contain the genetic information (genes) and are normally found in pairs in the nucleus (humans have 23 pairs). They are replicated every time a cell divides by mitosis.

Mitosis vs. Meiosis Mitosis: Meiosis:
21/11/2018 Mitosis: Used for growth and repair of cells Produces a “clone” Cells with identical number of chromosomes and genetic information are produced Meiosis: Used to produce gametes for sexual reproduction – occurs in the testes and ovaries Each daughter cell has half the number of chromosomes of the parent During meiosis copies of the genetic information are made and then the cell divides twice to form four daughter cells.

Sexual Reproduction 21/11/2018 The human egg and sperm cell (“GAMETES”) contain 23 chromosomes each and are created by meiosis. When fertilisation happens the gametes fuse together to make a single cell called a ZYGOTE. The zygote has 46 chromosomes (23 pairs) and continues to grow through mitosis, producing cells with the same genes.

Stem Cells A while ago we considered examples of specialised cells:
21/11/2018 A while ago we considered examples of specialised cells: White blood cell Egg cell (ovum) Ciliated epithelial cell Nerve cell (neurone) A “stem cell” is a cell that hasn’t yet become specialised and can be found in embryos or bone marrow. These cells can be used to treat certain conditions but the use of these cells is very controversial.

Should these embryos be treated as humans?
Stem cell research 21/11/2018 Stem cells are cells that have not yet specialised: These stem cells have the potential to develop into any kind of cell. In grown adults they can be taken from bone marrow or they can come from embryos from unused IVF treatments. They can be used to treat conditions such as paralysis. Embryo Egg and sperm Cloned embryos The ethical issue: Should these embryos be treated as humans?

Making decisions 21/11/2018 Some questions cannot be answered by science and need to be considered on ethical grounds. Factors that might influence a decision: Beliefs/religion What does “the right thing” mean? “Playing God” Risks – acceptable or unacceptable? Social and economic contexts

Boy or Girl? 21/11/2018 X X Y “Allele” XX XY Girl Boy

Boy or Girl? 21/11/2018 Mother Son Daughter Father

Key words Gamete Zygote Allele Dominant Recessive Homozygous
21/11/2018 Gamete Zygote Allele Dominant Recessive Homozygous Heterozygous This allele determines the development of a characteristic This is formed when an egg is fertilised by a sperm This allele will determine a characteristic only if there are no dominant ones This word refers to a pair of chromosomes being made of two different alleles of a gene An egg or a sperm are called this This word refers to a pair of chromosomes being made of two of the same alleles of a gene An alternative form of a gene

Words – twins, helix, amino, code, bases, proteins
21/11/2018 How genes work - DNA Some facts: - DNA has a “double ______” structure - This contains instructions on what a cell does, how the organism should work etc - The instructions are in the form of a ______ - The code is made up from the four ____ that hold the strands together - The bases represent the order in which _____ acids are assembled to make specific ________ - Everyone (apart from identical ______) has different DNA and people can be identified by “DNA finger printing” Words – twins, helix, amino, code, bases, proteins

What would the offspring have?
Eye colour 21/11/2018 In eye colour the brown eye allele is dominant, so we call it B, and the blue eye is recessive, so we call it b: BB Bb bb Homozygous brown-eyed parent Heterozygous brown-eyed parent Blue-eyed parent What would the offspring have?

X X Eye colour BB bb Bb Bb (FOIL)
21/11/2018 Example 1: A homozygous brown-eyed parent and a blue-eyed parent: Example 2: 2 heterozygous brown-eyed parents BB bb Bb Bb X X Parents: B b B b B b Gametes: (FOIL) Bb Bb Bb Bb BB Bb bB bb Offspring: All offspring have brown eyes 25% chance of blue eyes

Eye colour 21/11/2018 Example 3: A heterozygous brown-eyed father and a blue-eyed mother: Bb bb Equal (50%) chance of being either brown eyed or blue eyed. B b b Bb Bb bb bb

B b B b Bb bb Another method
21/11/2018 Example 3: A heterozygous brown-eyed father and a blue-eyed mother: B b B b Bb bb Father Mother

Example questions 21/11/2018 1) In mice, white fur is dominant. What type of offspring would you expect from a cross between a heterozygous individual and one with grey fur? Explain your answer with a genetic diagram. 2) A homozygous long-tailed cat is crossed with a homozygous short-tailed cat and produces a litter of 9 long-tailed kittens. Show the probable offspring which would be produced if two of these kittens were mated and describe the characteristics of the offspring (hint: work out the kitten’s genotype first).

X X Inherited diseases Ff Pp pp
21/11/2018 1) Cystic fibrosis – a disorder or cell membranes. It’s caused by recessive alleles so both parents need to be “carriers”: Ff X 2) Polydactyly – a condition where a person has extra fingers or toes. It’s caused by a dominant allele so can be passed on by a parent who already has it: Pp pp X Embryos can be screened for alleles that cause these diseases before birth.

Family Pedigree Charts
21/11/2018 21/11/2018 Consider the following chart of the offspring and grandchildren between two polydactyly carriers: Key: = male = female = P allele = p allele Q. Describe the genotype and the phenotype of each of the grandchildren. Also, which member of this family has got polydactyly?

21/11/2018 B2.8 Speciation

Fossils 21/11/2018 Fossils provide evidence of early life and could have been formed in many ways. Four examples: This fossil was formed by parts of its body being replaced by minerals This fossil of a bat was formed due to hard parts of the animal not decaying Fossilised footprints This bee and orchid pollen were preserved in amber – the amber lacked some of the conditions needed for decay to happen

The “Stenheim skull”, found in Germany in 1933
Fossil records 21/11/2018 Fossil records can provide a useful way of observing a species’ development: The “Stenheim skull”, found in Germany in 1933 Oh no… The problem is, many early forms of life only had soft bodies and the few remaining traces of them have been destroyed by geological activity. This makes it difficult for scientists to know what happened in the distant past.

Sabre-toothed tigers and mammoths
Extinct Species 21/11/2018 Sabre-toothed tigers and mammoths Dodo

Extinction 21/11/2018 Words to use: deforestation, competition, dinosaurs, human, environment Extinction can happen due to an organism’s inability to adapt and die because of: Increased _______ New predators Changes in the _________ New diseases Alternatively, a “mass extinction event” can happen, for example the extinction of the __________. In modern days animals are in danger due to _____ activity, e.g. pollution, hunting, __________ etc… Oh no…

Words – species, mutations, mountain, gene, ancestors, reproducing
Geographic isolation 21/11/2018 Different species can be formed by “geographic isolation”, for example, consider an African elephant: Elephants are separated by a geographic feature e.g. a _________ Elephants on each side of the mountain have different ______ in their _____ pool Some offspring have characteristics that help them survive Their weaker _______ die out and the offspring are so genetically removed that they’re incapable of ________ with each other – they’re now different ________ Words – species, mutations, mountain, gene, ancestors, reproducing

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