Essay on Tatee: Photosynthesis and Light Intensity

Submitted By Bisma0406
Words: 8735
Pages: 35

A2 level Biology notes

Unit 4- Populations and the Environment

1. Populations 3 1.1 Populations and ecosystems 3 1.2 Investing populations 3 1.3 Variation in population size 5 1.4 Competition 6 1.5 Predation 8 1.6 Human populations 10
2. ATP 12 2.1 Energy and ATP 12
3. Photosynthesis 14 3.1 Overview of Photosynthesis 14 3.2 The Light- dependent reaction 16 3.3 The Light Independent Reaction 17 3.4 Factors Affecting Photosynthesis 18
4. Respiration 20 4.1 Glycolysis 20 4.2 Link reaction and Krebs cycle 21 4.3 The electron transport chain 23 4.4 Anaerobic respiration 24
5. Energy and Ecosystems 25 5.1 Food chains and Food webs 25 5.2 Energy Transfer between Trophic Levels 26 5.3 Ecological Pyramids 27 5.4 Agricultural Ecosystems 28 5.5 Chemical and Biological Control of Agricultural Pests 29 5.6 Intensive Rearing of Domestic Livestock 31
6. Nutrient Cycles 33 6.1 The carbon cycle 33 6.2 The greenhouse effect and global warming 34 6.3 The Nitrogen Cycle 35 6.4 Use of Natural and Artificial Fertilisers 36 6.5 Environmental consequences of using nitrogen fertilisers 36
7. Ecological Succession 37 Succession 37 7.2 Conservation of Habitats 38
8. Inheritance and Selection 39 8.1 Studying inheritance 39 8.2 Monohybrid Inheritance 40 8.3 Sex Inheritance and Sex Linkage 41 8.4 Co-dominance and Multiple Alleles 42 8.5 Allelic Frequency and Population Genetics 43 8.6 Selection 44 8.7 Speciation 45

1. Populations
1.1 Populations and ecosystems

❖ Ecosystem- It is made up of all the interacting biotic and abiotic features in a specific area ❖ Population- A group of interbreeding organisms of one species in a habitat. ❖ Community- All the populations of different organisms living and interacting in a particular place at the same time. ❖ Habitat -The place where a community of organisms lives. ❖ Ecological niche- All the biotic and abiotic conditions required for an organism to survive, reproduce and maintain a viable population. No 2 species occupy exactly the same niche.

1.2 Investing populations

❖ To study habitat often necessary count no individuals of species in given space ❖ This known as abundance ❖ Virtually impossible identify & count every organism ❖ Do so would time consuming & cause damage habitat being studied ❖ SO small samples usually studied in detail ❖ As long as samples representative of habitats as whole any conclusion drawn from findings will be valid ❖ No sampling techniques used in study of habitat, these include: ➢ Random sampling using frame or point quadrats ➢ Systematic sampling along transects
Quadrats
❖ Three factors to consider when using quadrats: ❖ Size quadrat use: depend upon size plants or animals being counted & how they distributed within area. Large species = larger quadrat ➢ Where species occurs in series group rather being evenly distributed throughout area, a large no small quadrats will give more representative results than small no large ones ❖ No of sample quadrats to record within the study area: larger no of sample quadrats the more reliable results will be. ➢ Recording species w/in quadrat is time-consuming task, needs balance between validity results & time available. ➢ Greater no different species present in area studied = greater no quadrats required valid results ❖ Position each quadrat w/in study area: produce statistically significant results technique random sampling must used.
Random Sampling ❖ Important sampling random avoid any bias in collecting data, avoiding bias ensures data obtained valid ❖ A good method of random sampling is to: 1. Lay out two long tape measures @ right angles, along 2 sides of study area 2. Obtain series of…