N 5 Biology Unit 3 Life on Earth

N 5 Biology Unit 3: Life on Earth Lesson 3: Algal Blooms KA 5: Food Production

Learning Intentions At the end of this lesson I should be able to: § Describe the effects of fertilisers leaching into fresh water. § Give examples of ways to reduce the problems caused by fertilisers. #Food. Production

Fertilisers § Fertilisers are chemicals rich in nitrate and other substances ( e. g. phosphate, magnesium). § Nitrates are needed to produce amino acids which make up proteins. Therefore they are essential for plant growth. § Without nitrates, plant growth would be reduced and the leaves would be yellow.

Problems with Fertilisers • What do you think would happen if fertilisers were accidently put into a river or a lake? • If leached into a water ecosystem, fertilisers encourage excessive growth of algae - causing an algal blooms.

Algal Blooms

Algal Blooms 1. Fertilisers dissolve in rainwater and leach from the fields into rivers and lochs giving extra unwanted nitrates. 3. This reduces light levels killing aquatic plants. 2. Algae population increases causing algal bloom. 4. These dead plants, as well as dead algae, become the food for bacteria which increase greatly in number. 5. The bacteria use up large quantities of oxygen reducing the oxygen available for other organisms.

Algal Bloom Steps 1. Fertilisers dissolve in rainwater and leach from the fields into rivers and lochs giving extra unwanted nitrates. 2. Algae population increases causing algal bloom. 3. This reduces light levels killing aquatic plants. 4. These dead plants, as well as dead algae, become the food for bacteria which increase greatly in number. 5. The bacteria use up large quantities of oxygen reducing the oxygen available for other organisms.

Problems with Fertilisers § Fertilisers can result in algal blooms which cause harm to the plants and animals in an ecosystem. § We can reduce the problems caused by using fertilisers with the following methods: - Use natural fertilisers like manure and compost which do not dissolve easily in rainwater. - Use of Genetically modified crops.

Genetically Modified (GM) Crops • Crops which have had their genes altered to confer an advantage. • Disease-resistant genes • Increased growth rates • Toxins to ward off insect pests (harmless to humans). • Some people worry about unforeseen consequences of altering genes….

Questions 1. Explain why fertiliser needs to be added to land where a crop is repeatedly grown, harvested and removed. 2. What events lead to the formation of an algal bloom. 3. Why does an algal bloom lead to a reduction in oxygen content of the water in the affected ecosystem? 4. Give an example of a method which could be used to reduce the problems caused by using fertilisers.

Answers 1. Fertiliser is needed because natural cycles have been broken with the result that almost no dead material is returned to the soil for breakdown by micro-organisms and release of nitrates into the soil by natural means. 2. Excessive fertiliser is leached into a loch or a watercourse making the water rich in nutrients. This promotes rapid growth of algae, which form a bloom. 3. When the algae die they are decomposed by bacteria, which in turn use up much of the aquatic ecosystems dissolved oxygen supply during respiration. 4. Use of natural fertilisers which do not dissolve easily in water or use of GM crops.

Success Criteria I should now be able to: § Describe the effects of fertilisers leaching into fresh water. § Give examples of ways to reduce the problems caused by fertilisers. #Food. Production

Starter Questions 1. Explain i) what is meant by an algal bloom and ii) the reason that they are caused. 2. Give one way that an algal bloom effects an aquatic ecosystem. 3. Give an example of a method which could be used to reduce the problems caused by using fertilisers.

N 5 Biology Unit 3: Life on Earth Lesson 4: Use of Pesticides KA 5: Food Production

Learning Intentions At the end of this lesson I should be able to: § Describe the effects of pesticides on food chains. § Suggest possible alternatives to the use of pesticides. #Food. Production

What are Pesticides? • Pesticides are chemicals that are sprayed onto crops to protect them from disease and other organisms. • Pesticides include: 1. Herbicides are used to kill plants 2. Fungicides are used to kill fungal infections 3. Insecticides are used to kill insects 4. Bactericides are used to kill bacteria

Pesticides • A good pesticide is bio-degradable. This means that they are capable of being broken down by bacteria and other organisms – thus preventing pollution. • If a pesticide is non-biodegradable, it can persist in the environment for a very long time and accumulate in the bodies of organisms further up a food chain. • An example of a non-biodegradable pesticide is: DDT.

Bioaccumulation of DDT (dichlorodiphenyltrichloroethane) During the 1960’s, fish eating birds such as cormorants and osprey declined dramatically in numbers. It was discovered that a pesticide (DDT) became magnified in food webs and made their egg shells too fragile for survival.

Use of Pesticides § Pesticides are chemicals that are sprayed onto crops to protect them from disease and other organisms. § Pesticides sprayed onto crops can accumulate in the bodies of organisms over time. § As they are passed along food chains, they accumulate and so toxicity increases and can reach lethal levels. This is called Bioaccumulation

Use of Pesticides Plankton LOW Smaller Fish Larger Fish Increasing pesticide toxicity Osprey HIGH (lethal)

Use of Pesticides § The following alternatives can be used to avoid the problems caused by pesticides: - Use of biological controls (introduce natural predators or diseases into an ecosystem). - Use of GM crops which can produce their own toxins to resist insects.

Recap Questions 1. Describe how bioaccumulation of pesticides can be lethal to organisms at the TOP of a food chain. - Pesticides can accumulate with increasing toxicity as they rise up the food chain, eventually resulting in death. 2. Suggest 2 alternatives to avoid the use of pesticides. - Biological Controls - GM Crops

Success Criteria I should be able to: § Describe the effects of pesticides on food chains. § Suggest possible alternatives to the use of pesticides. #Food. Production

Starter Task 1. What are fertiliser's used for? 2. What are pesticides used for? 3. Name 1 environmental problem caused by pesticides. 4. Describe 2 ways to over come pesticide use.

N 5 Biology Unit 3: Life on Earth Lesson 1: Mutations KA 6: Evolution of a Species

Learning Intentions At the end of this lesson I should be able to: § Explain what is meant by the terms mutation, genotype and phenotype. § Give examples of environmental factors that can increase mutation rates. § State that mutations can be neutral, or cause an advantage/disadvantage. #Evolution

Making proteins from DNA (instructions) Amino Acids Proteins

When a Mutation occurs… Proteins Instructions change

Mutation § A mutation is the random change to an organism’s DNA. § Mutations can be an advantage or disadvantage to survival, or they can be neutral. § Mutations are spontaneous and are the only source of new alleles.

Mutagenic Agents § The rate of mutations can be increased by mutagenic agents. § Examples include: - Radiation (UV Light, X-ray, Gamma…) - Chemical (Mustard gas, cigarettes…) § Most mutations are harmful to survival, however some mutations are neutral. Very rarely do mutations confer an advantage to survival.

Advantageous Mutations Natural Defences (spikes…) Long-necked giraffes

Mutations • https: //www. youtube. com/watch? v=m_l. L Wgq. KUp 4 • 5 minutes, 48 seconds

Success Criteria I should now be able to: § Explain what is meant by the term mutation, phenotype and genotype. § Give examples of environmental factors that can increase mutation rates. § State that mutations can be neutral, or cause an advantage/disadvantage. #Evolution

Starter Task 1. Explain what is meant by the following terms: - Mutation - Mutagenic agent 2. Name 2 mutagenic agents.

N 5 Biology Unit 3: Life on Earth Lesson 2: Adaptations & Variation KA 6: Evolution of a Species

Learning Intentions At the end of this lesson I should be able to: § State that variation within a population allows evolution over time. § Describe the adaptations of different organisms to suit their environments. #Evolution

Variation in a Species

Variation • Variation means a difference in phenotype. • Mutation is what causes variation within a population. • Variation within a population makes it possible for a population to evolve over time in response to changing environmental conditions. Different Phenotypes

Adaptations • Variation within a population makes it possible for a population to evolve over time in response to changing environmental conditions. • New alleles (genes) produced by mutation allow plants and animals to adapt to their environment. • Adaptations give an organism an advantage which increases their chances of survival. An adaptation is an inherited characteristic that makes an organism well suited to survival in its environment.

Research Task What adaptations do each of these organisms have that allow them to survive in their environment?

Success Criteria I should now be able to: § State that variation within a population allows evolution over time. § Describe the adaptations of different organisms to suit their environments. #Evolution

N 5 Biology Unit 3: Life on Earth Lesson 3: Natural Selection KA 6: Evolution of a Species

Learning Intention At the end of this lesson I should be able to: § Explain what is meant by survival of the fittest. § Describe the process of natural selection with use of an example organism.

Natural Selection § A species produces more offspring than the environment can support. § This leads to a struggle for survival. What factors may influence an organisms ability to survive?

Selection Pressures Only rabbits with the best characteristics will survive to pass on their genes. Exposure -Thinner coats - not good at competing for shelter Starvation - Not good at competing for food Predators -poorly camouflaged -slow reactions Disease -weaker offspring

Survival of the Fittest § Organisms whose phenotypes are better adapted to their environment have a better chance of survival. § This means they can reach reproductive age and pass on the favourable alleles (genes) to their offspring. § Over many generations the poorer members are selected against and are weeded out. § This process is known as Natural Selection.

On the Origin of Species • Natural Selection was first proposed by Charles Darwin in 1859! • He suggested that a combination of Natural Selection, mutation and selection pressures explained biodiversity through his theory of evolution. Charles Darwin (1859)

Theory of Natural Selection 1. Variation exists between members of the species and they compete for survival. 2. The best adapted individuals in the population survive and reproduce to pass on their favourable alleles to offspring. 3. These alleles increase in frequency within the population and the species change over time.

Survival of the Fittest • http: //www. bbc. co. uk/learningzone/clips /natural-selection-and-survival-of-thefittest/5516. html • 1 minute 57 seconds

Natural Selection in Action: The Peppered Moth • Two forms of the peppered moth exist: – Light form (dominant) – Dark form (arose by mutation) Non-polluted area Area of high air pollution

Natural Selection in Action: Giraffes • Two forms of giraffe used to exist: – Short necked giraffe (dominant) – Long necked giraffe (arose by mutation) Short necks Long necks

Galapagos Islands’ Finches (Darwin’s Finches) • In 1835 Darwin visited the Galapagos islands. • Natural selection in action can be shown by studying this.

Natural Selection: Exam Question Explain the process of natural selection in the context of one of the following organisms: 1. Peppered moths in an area of high pollution (light vs dark) 2. Giraffes (short neck vs long neck) 3. Galapagos finches (Beak shape and size)

Model Answer 1 • Peppered moths are produced in 2 forms: light form and dark form. A struggle for survival occurs. • The dark moths are the best adapted because of their camouflage to the polluted area and so they survive to reproduce. • They pass on their advantageous alleles (dark colour) to the offspring and this allows the species to change over time.

Model Answer 2 • There are two types of giraffes: short neck and long neck. A struggle for survival occurs. • The long necked giraffes are the best adapted because they have access to more food and so they survive to reproduce. • They pass on their advantageous alleles (long neck) to the offspring and this allows the species to change over time.

Model Answer 3 • Many finches are produced with varying beak shapes and sizes. A struggle for survival occurs. • The best adapted finches have the beaks which allow them to get the most food and survive to reproduce. • They pass on their advantageous allele (beak size/shape) to the offspring and this allows the species to change over time.

Success Criteria I should now be able to: § Explain what is meant by survival of the fittest. § Describe the process of natural selection with use of an example organism.

N 5 Biology Unit 3: Life on Earth Lesson 4: Speciation KA 6: Evolution of a Species

Learning Intentions At the end of this lesson I should be able to: § State what is meant by a species. § Describe how mutations and natural selection leads to speciation.

What is a Species? • A species is a group of genetically similar organisms that are able to interbreed to produce fertile offspring. Puppy (Fertile) Mule (Sterile)

Liger Video • http: //www. youtube. com/watch? v=1 z. OWYj 59 BXI • 4 minutes 30 seconds Liger (sterile)

Speciation § Speciation is the formation of new species. § It occurs when a population becomes isolated from other populations of the same species and mutation occurs. § Isolation barriers can be: - geographical (e. g. river, mountain) - ecological (e. g. p. H, temperature, humidity) - behavioural (e. g breeding cycles out of rhythmn)

Speciation

A population becomes isolated by an isolation barrier Different mutations occur in each sub-population. Natural selection selects for different mutations in each group, due to different selection pressures. Each sub-population evolves until they become so genetically different they are two different species.

Speciation Videos • Speciation song: https: //www. youtube. com/watch? v=WD Ps. ZPKSEFg (1 minutes, 39 seconds) • Speciation tutorial: • https: //www. youtube. com/watch? v=PKb 8 Yi 5 xzh. E (3 minutes, 49 seconds)

Starter Task 1. Explain what is meant by the term species. 2. Give the term that is used to describe the process that allows a new species to develop. 3. Name the 3 types of isolation barriers.