National 5 Biology Unit 3 Notes

Alternative transcript:

fox now only has one type of prey to feed on. However, the population of caterpillars & wood mice would increase as the rabbits are gone which means more food (green plants). NOTE: The arrows in a food web shows the the direction of energy flow (Ch.4) c. Ecological niches ● ● Niche: The role of an organism within an ecosystem. An organism's niche could be described by its role in predator-prey interactions / how it competes with other organisms for the same (or similar) resources that are limited in supply. d. Competition Occurs when organisms require the same / similar resources that are limited in supply (e.g water, food supply, mates). There are 2 type of competition ○ Interspecific competition ○ Intraspecific competition Interspecific competition O Occurs between individuals of different species that require similar resources within an ecosystem. o Example: Lions & Hyenas compete for similar species of prey. • Intraspecific competition O Occurs between individuals of the same species who require the same resources. This type e of competition is more intense as they are all competing for the same O resources. O The consequences of intraspecific competition is that not all varieties of individuals will be able to pass down their alleles. a. Biotic & Abiotic Factors ● There are 2 type of factor that can affect the life of organisms/ O Abiotic (nonliving factors) O Biotic (factors linked to interactions between living things) Example Grazing Predation Food availability Disease Competition b. Measuring abiotic factors pH Temperature Biotic Ch2. Distribution of Organisms Light intensity Soil moisture Abiotic factors are nonliving factors such as temperature & light intensity. The reliability of the results can be checked by taking many samples. Factor Equipment used Thermometer (soil / water) pH Temperature Moisture Rainfall Light intensity Light metre pH metre / pH indicator Moisture metre Abiotic How to use Insert probe into soil / water & wait until the reading is stable. pH metre: Insert probe into soil & read from the scale. Hold the panel towards light & read from the scale. Make sure not to cast shadow over the panel. Insert probe into soil & read from the scale. Make sure to wipe the probe before taking another reading. This ensures that the new reading isn't affected by previous measurements. c. Sampling plants & animals Pitfall traps (Animal sampling) Used to sample small invertebrates organisms that live on the surface of the soil. ● ● ● Don't put a lid over the trap or no organisms are able to fall into the trap, however to prevent birds eating the specimens cover the trap with a raised stone / leaf. Place the trap aligned with the soil surface. The trap gives an approximation of an organism's abundance in the environment. In some traps, people would add ethanol into it to prevent specimens from eating each other. • If the number of pitfall traps placed are low, then the result may not be reliable to represent the area as a whole. Preservative: 50% ethanol to preserve specimens and stop them eating each other Leaf or stone ROOF raised from soil surface to allow organism to crawl in and hide from birds Container (e.g cup) in soil to catch organisms, top of container should be in line with soil surface Quadrat (Plant sampling) Used to sample small, low-growing plants / slow moving organisms & to estimate the total number of plants in a given area. Usually 50cm² / 1m² size. There are 2 types of quadrat: When taking samples using a quadrant, it needs to be randomly placed within the area. ● The randomness is important if a truly representative estimate of abundance of the different organisms is to be obtained. • If a plant lies underneath the outside frame of the quadrat, it can be recorded or not, depending on the rules that were set beforehand. These rules must constantly be followed through the whole investigation. ● If the number of quadrat placed is low, then the result may not be reliable to represent the area as a whole. NOTE: Repeat, Random & Representative Results d. Paired -Statement Keys ● Used to identify which species the sample organisms belong to. ● The statement is made about the physical characteristics of an organism. ● After answering a statement, it should either direct you to another statement / the organism is identified & the name of the species is given. ● Need to avoid making the statement ambiguous / subjective. ● Example Predation 1. Fur present: Fur absent: 2. Feathers present: Feathers absent: 3. Smooth skin present: Smooth skin absent: 4. Gills present: Gills absent: O Mammal Go to Question 2 This can impact many species in an ecosystem. Bird Go to Question 3 e. Effect of abiotic & biotic factors on the distribution of organisms Amphibian Go to Question 4 Fish Reptile Predation: When one organism (predator) hunt, kills & feed on another organism (prey) Example: O In Scotland wolves were the natural predator of red deer. O However, wolves are now extinct from Scotland therefore the red deer don't have any natural predators causing their population to increase. The result of the red deer population increasing is some areas being over-grazed, which reduces plant species diversity. o To prevent further decrease in plant species diversity, culls (killing deers to reduce their number) is carried out to reduce the impact on the environment. Grazing ● Grazing: When herbivores feed on plants. At low grazing level, plant species diversity is low as a few dominant species will prevent others plants from growing there. ● At higher grazing level, plant species diversity increases as the dominant species is primarily eaten by the herbivores, keeping their excessive growth in check & giving opportunity for other plants to grow. • However, if grazing levels get too high, plant species diversity will decrease as all the plants are greatly fed upon & some species will become extinct in that area. Temperature Number of plant species Low High Grazing intensity ● Earth's temperature varies greatly. Very high Animals are adapted to the temperature they survive in. For example, polar bears have thick, white furs to survive in cold weather. pH • pH can affect which organisms can survive in a particular ecosystem. • Acid rain is formed when fossil fuels are burned & gases such as lphur dioxide are produced. It can cause damage to forests such as the Black Forest in Germany. f. Indicator species Def: A species that by its presence or absence shows the environmental conditions of an area. Example: Certain species of lichen cannot grow if the air pollution levels are too high. Therefore if that species of lichen is present in an area it indicates that the air pollution is low in that area. a. Green plants & producers. Greens plants are called producers as they produce food inside their cells through simple chemicals as raw materials. ● Ch3. Photosynthesis Food produce by green plants are called carbohydrates (chemicals contain carbon, hydrogen & oxygen) • Sunlight provides the energy to combine raw materials into the final product, sugar. The raw materials that's required for photosynthesis are water (H₂O) from the soil & CO₂ from the air. b. Chlorophyll Found in chloroplast Chlorophyll can capture sunlight which is required for photosynthesis & converts it to chemical energy. ● Some plants have variegated leaves, which means in some areas contain chlorophyll & will present the colour green, while some areas don't contain chlorophyll & will present white / yellow colour. c. Stages of photosynthesis • Simple & summary form equation of photosynthesis Raw materials carbon dioxide Stage 1: Light Reactions water ● Occurs in the chloroplast. Conditions Stage 2 Carbon fixation Chlorophyll Diffuses out of chloroplast light chlorophyll • Sunlight is absorbed by chlorophyll which is in the chloroplast & converted to chemical energy. The chemical energy is then transferred to ATP (ADP + Pi). Some of the chemical energy is used to split water molecules into hydrogen & oxygen. • Oxygen isn't needed in photosynthesis therefore it's a waste product & will diffuse out of the plant cell from out of the plant through the stoma. • Hydrogen, ATP formed is required in the next stage of photosynthesis. Oxygen glucose Light energy Chemical energy Water Products Hydrogen ADP ATP + Pi oxygen Passed to second stage of photosynthesis • A series of enzyme controlled reactions using ATP from light reactions to combine hydrogen (from light reactions) with carbon dioxide & form sugar (glucose). Enzymes Hydrogen (from stage one) Uses of sugar + Carbon dioxide Chemical energy stored in sugar is released by respiration. • Sugar can also be used to build up other plant materials such as cellulose & starch. d. Limiting factors of photosynthesis ● Limiting factors that can affect the rate of photosynthesis: O Water & carbon dioxide concentration o Light intensity o ATP (from stage one) Temperature (enzyme reaction) rate of photosynthesis If the quantity of a limiting factor increases, the rate of photosynthesis will increase as well. The rate of photosynthesis can be estimated using the following measurements: o The rate of oxygen production O The rate of carbon dioxide taken in by plant O The rate of carbohydrate production light intensity Sugar 30°C 20°C At X: Light intensity is limiting the rate of photosynthesis At Y: Temperature is limiting the rate of photosynthesis. Light is not the limiting factor because when the light intensity is increased the rate of photosynthesis stays the same Ch4. Energy in ecosystem a. Food webs FOX CHAFFINCH + RABBIT CATERPILLAR GREEN PLANTS SPARROWHAWK LADYBIRD GREENFLY OAK TREE Plant material HEDGEHOG WOODMOUSE There's a progressive loss of energy at each stage in a food chain. In food web & chains, the arrows show the direction of energy flow when one organism consumes another organism. Not all energy is passed on to the next stage in a food chain/web. • Energy is lost as heat, movement, & undigested materials. SONG THRUSH BEECH TREE Herbivore EARTHWORM Fungi & bacteria are decomposer, which means they decompose the undigested materials left by other organisms. Only a small amount of energy an organism gains through consuming other plants / organisms was originally used for growth (around 10%). Growth (10%) Undigested materials (60%) Heat and movement (30%) ● This means that if there's 1kg of food, only 100g is actually absorbed by the consumer's body. Wheat 1kg Wheat Cow 1kg 100g As more levels are in a food chain, the more energy is lost in every level. b. Pyramids of numbers & energy • Therefore, the shorter the food chain is, the more efficient it is as there is less energy being lost before it reaches the top level. Pyramids of numbers • Represents the number of organisms at each level. Decreasing numbers Decreasing numbers Human 100g Tertiary Consumers Secondary Consumers Primary Consumers Producers Human 10g • Usually this wide-base shape is most common, with a large number of producers & gradually decreasing as it moves up the food chain. However, if the producer has a very large mass (e.g tree) & is able to store enough energy to support a larger number of smaller consumers, the pyramids will show an irregular shape. Sparrowhawk etc. Blue Tit, Chaffinch etc. Beetles, Ladybirds etc. Aphids and Caterpillars etc. Oak tree Pyramids of energy ● Shows the quantity of energy stored in the biomass of the organisms at each level in a food chain. ● Decreasing energy Pyramids of energy will always have a wide-base shape as energy is always lost between each level of the food chain. Fish Copepods Primary Consumers - Zooplankton Producers - Phytoplankton NOTE: Pyramids of numbers don't show how much energy is stored in the organisms at each stage. It only shows the number of the individuals. a. Human population & food supply ● b. Nitrates • Nitrogen is essential for the formation of amino acids which are then formed into proteins. ● ● However, nitrogen cannot be directly used by plants to make amino acids. • Only nitrates are useful to plants, therefore it requires other processes to convert nitrogen gas to nitrates in the soil. ● As the human population increases, the demand for food has also increased. Ch5. Food production Therefore, farm increase the amount of crop yields by: o Using fertilisers to ensure crops have enough nutrients for growing quickly. o Using pesticides to ensure pests don't decrease the number of crop yields. ● ● Animals make protein by using the amino acids from digesting plant proteins. ● NOTE: ● Plants absorb nitrates that have dissolved into soil. Fertilisers can be added to the soil to increase the concentration of nitrate in the soil. c. Fertilisers Nitrates are soluble in soil Nitrate comes from breaking down organic materials, or from adding fertilisers containing nitrates. Fertilisers can increase the levels of nitrate & other nutrients in the soil so that plants are able to get the nutrients they need to grow quickly. However, fertilisers added to the soil can leach into nearby water. ● The sudden increase of nitrate levels causes the algae present in the water to multiply rapidly increasing their population (this is referred to as algae bloom). The consequences of an algae bloom can be summarised in the following stages: 1. Algae blocks light & other plants die as there's no sun to photosynthesis. 2. Dead plants & dead algae are food for decomposers (bacteria) 3. The amount of oxygen decreases again as bacteria also requires oxygen for aerobic respiration. 4. Finally, the level of oxygen is too low for any organisms to survive there & there's a loss of biodiversity in the ecosystem. Alternatives to fertilisers GM crops can be used to decrease the amount & concentration of fertilisers used, because GM crops have certain genes added to them to increase the production / quality of it. d. Pesticides Pesticides are sprayed onto crop plants to kill pests. Some pesticides aren't biodegradable (aren't able to dissolve naturally). ● As a result, some pesticides' toxic substances can accumulate in the organisms' body. The increase of the toxicity concentration inside an organism is called bioaccumulation (bio:accum:ulation) ● Bioaccumulation can result in biomagnification (don't need to learn this term yet) the increase of toxicity at higher levels of a food chain. ● The toxicity of pesticides can be lethal to organisms at the top of the food chain. Pesticide in great blue heron 25 ppm Pesticide in sunfish 2 ppm Pesticide in mayfly nymph 0.5 ppm Pesticide in algae 0.04 ppm Pesticide in water 0.000003 ppm ↑ Concentration of pesticide increases ten million times Alternatives to using pesticides GM crops are inserted with genes from bacterias which can generate proteins that create toxic to certain insect species. Therefore less pesticides are used. ● ● Biological control is also an alternative to using pesticides to reduce the number of pest. • Biological control includes: o Introducing a predator which prey on the pests' species. (The predator is called a biological control agent) o o Using parasite Using pathogens. a. Mutations Def: The changes to an organism's genetic material (sequences of DNA bases). ● Ch6. Evolution of Species Mutations are spontaneous & random. ● Mutations are the only source of new alleles in a population. Some mutations give an organism an advantage by improving their phenotype to be more well adapted with the environment they live in. But some mutations give a disadvantage to an organism. For example ; causing a change to an essential enzyme. Some mutations will have no effect on the organism's chance of survival / reproduction are classed as neutral mutations. Organisms with an advantageous mutation will be more likely to pass on their allele to their next generation. • Organisms with a disadvantageous mutation (e.g Sickle cell mutation) will have less chance of survival & less chance to pass on their allele. O Sickle cell mutation isn't all bad, people with this mutation have some resistance to the parasite that causes malaria. Variation in a population allows some individuals to survive & reproduce even if the environment changes. ● Environmental factors such as radiation / some chemicals (e.g Mustard gas) can increase the rate of mutation. ● These factors are known as mutagenic agents. XXXX Original MXX !!!!! Mo Voix Correct copy Original LOL Mutant copy b. Natural Selection ● Variation allows a population as a whole to adapt to changes in its environment over time. Adaption is an inherited characteristic which can be passed down on organism to be more well suited to survive in its environment. Factors such as predation, food/ disease which make some individuals better surviving to reproduce than others are known as environmental selection] pressure. The individuals that are the most adapted to the selective pressures will be able to survive to reproductive age & pass on the alleles that give them the selective advantage to their offsprings. The alleles which gave selective advantage will have an increase in the population while the alleles that make them less well-adapted will decrease in the population. Yum! Green beetles! Our favorite! * ...generations later... ...generations later... Green beetles have been selected against, and brown beetles have flourished. c. Speciation • Species: A group of organisms that can interbreed to produce fertile offspring. ● Formation of new species is called speciation. Speciation occurs in a certain sequence: 1. Individuals in a population are able to interbreed freely 2. An isolation barrier causes the population to separate (forming subpopulation) & unable to interbreed freely. 3. Different mutations occur in each subpopulation. 4. Natural selection occurs with different selection pressures on each subpopulation. Changing the subpopulation over many generations. 5. If the isolation barrier is removed & the subpopulations can no longer interbreed with each other to produce a fertile offspring, speciation has occurred. ● The subpopulations are unable to produce fertile offspring because each subpopulation is now so genetically different from each other that interbreeding isn't biologically possible. Isolation Barrier • Splits a population into sub-population. Isolation barrier can be due to different reasons such as: • Ecological o o Individuals don't encounter each other due the differences in their ecological niches Example: The habitat of the population contains 2 types of food & individuals either feed on one type / the other. Individuals that feed on one type of food may never encounter individuals that feed on the other type of food so they are isolated from each other. Geographical O Oceans, mountains, desert Behavioural O Individuals don't breed with each other as a result of differences in their behaviours o Example: Some females in a population prefers to mate with one variety of males & other prefers others.