Hero image

Paperfriendlyresources's Shop

Average Rating4.27
(based on 235 reviews)

Paperfriendlyresourcesuk New Resources Coming soon! PFR resources have been designed to ensure good quality teaching is not compromised by printing restrictions or buffering videos. Lessons that include worksheets have been created for teachers to print at least two copies to an A4 sheet.

371Uploads

320k+Views

260k+Downloads

Paperfriendlyresourcesuk New Resources Coming soon! PFR resources have been designed to ensure good quality teaching is not compromised by printing restrictions or buffering videos. Lessons that include worksheets have been created for teachers to print at least two copies to an A4 sheet.
AQA new specification-The history of genetics-B15.1
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-The history of genetics-B15.1

(0)
The history of genetics lesson created in accordance to the NEW AQA Specification (9-1). Designed for a separates class. Includes: embedded videos and timers, slide animations, practice questions with answers on slides, worksheet and an interactive quiz. NB: If you are unable to play videos a URL link can be found in the slide notes. AQA spec link: 4.6.3.3 Relevant chapter: B15 Genetics and evolution. AQA Biology trilogy edition textbook-Page 234-235 Students are required to know the following; Students should be able to: • describe the development of our understanding of genetics including the work of Mendel • understand why the importance of Mendel’s discovery was not recognised until after his death. In the mid-19th century Gregor Mendel carried out breeding experiments on plants. One of his observations was that the inheritance of each characteristic is determined by ‘units’ that are passed on to descendants unchanged. In the late 19th century behaviour of chromosomes during cell division was observed. WS 1.1 Our current understanding of genetics has developed over time. In the early 20th century it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways. This led to the idea that the ‘units’, now called genes, were located on chromosomes. In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out. This scientific work by many scientists led to the gene theory being developed.
AQA new specification-Growing bacteria in the lab-B5.3
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Growing bacteria in the lab-B5.3

(0)
NB: This is a BIOLOGY (SEPARATES) ONLY lesson Growing bacteria in the lab lesson created in accordance to the NEW AQA Specification (9-1). Includes: slide animations, embedded videos, differentiated questions and answers have also been included within the slides. This resource is NOT suitable for combined science students. AQA spec link: 4.1.1.6 Relevant chapter: B5-Communicable diseases . AQA Biology third edition textbook-Page 78-79. Bacteria multiply by simple cell division (binary fission) as often as once every 20 minutes if they have enough nutrients and a suitable temperature. Bacteria can be grown in a nutrient broth solution or as colonies on an agar gel plate. Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics. Students should be able to describe how to prepare an uncontaminated culture using aseptic technique. They should be able to explain why: • Petri dishes and culture media must be sterilised before use to kill unwanted microorganisms • inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame • the lid of the Petri dish should be secured with adhesive tape to prevent microorganisms from the air contaminating the culture, and stored upside down • in school and college laboratories, cultures should be incubated at a maximum temperature of 25 °C.
AQA new specification-The human Kidney-B12.3
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-The human Kidney-B12.3

(4)
The human Kidney lesson created in accordance to the NEW AQA Specification (9-1) for my separates class (Year 10-KS4). This is a printer friendly resource it includes an: embedded video, slide animations and a mini exam question. As i taught this lesson in two parts it's only fair i upload the other presentation also (2 for the price of 1). **Knowledge of other parts of the urinary system, the structure of the kidney, and the structure of a nephron is not required.** AQA spec link: 5.3.3 Relevant chapter: B12-Homeostasis in action. ( Note: This topic is for BIOLOGY only not for combined science students). AQA Biology third edition textbook-Page 185-186 *The new specification requires students to know the following; Students should be able to describe the function of kidneys in maintaining the water balance of the body. The kidneys produce urine by filtration of the blood and selective reabsorption of useful substances such as glucose, some ions, And water. Knowledge of other parts of the urinary system, the structure of the kidney, and the structure of a nephron is not required. Students should be able to translate tables and bar charts of glucose, ions, and urea before and after filtration. Students should be able to describe the effect of ADH on the permeability of the kidney tubules. The water level in the body is controlled by the hormone ADH which acts on the kidney tubules. ADH is released by the pituitary gland when the blood is too concentrated and it causes more water to be reabsorbed back into the blood from the kidney tubules. This is controlled by negative feedback.
AQA new specification-REQUIRED PRACTICAL 6-Photosynthesis-B8.2
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-REQUIRED PRACTICAL 6-Photosynthesis-B8.2

(1)
Photosynthesis required practical (RP 6). This practical was completed in one lesson, students were asked to construct a graph from their data for homework. AQA spec link: 4.4.1.1 Relevant chapter: B8 Photosynthesis. AQA Biology third edition textbook-Page 126-127 Students are required to know the following; investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed. AT skills covered by this practical activity: AT 1, 2, 3, 4 and 5.
AQA new specification-Genetic engineering B13.4
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Genetic engineering B13.4

(1)
Genetic engineering lesson created in accordance to the NEW AQA Specification (9-1). Designed for higher ability (trilogy/combined) class, although content can be adjusted to suit any ability. Includes: embedded videos and timers, slide animations, practice questions with answers on slides, worksheet and an interactive quiz. NB: If you are unable to play videos a URL link can be found in the slide notes. AQA spec link: 4.6.2.4 Relevant chapter: B13 Variation and evolution. AQA Biology trilogy edition textbook-Page 184-185. Students are required to know the following; Students should be able to describe genetic engineering as a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic. Plant crops have been genetically engineered to be resistant to diseases or to produce bigger better fruits. Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes. Students should be able to explain the potential benefits and risks of genetic engineering in agriculture and in medicine and that some people have objections. In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms. Crops that have had their genes modified in this way are called genetically modified (GM) crops. GM crops include ones that are resistant to insect attack or to herbicides. GM crops generally show increased yields. Concerns about GM crops include the effect on populations of wild flowers and insects. Some people feel the effects of eating GM crops on human health have not been fully explored. Modern medical research is exploring the possibility of genetic modification to overcome some inherited disorders. (HT) Students should be able to describe the main steps in the process of genetic engineering. In genetic engineering: • enzymes are used to isolate the required gene; this gene is inserted into a vector, usually a bacterial plasmid or a virus • the vector is used to insert the gene into the required cells • genes are transferred to the cells of animals, plants, or microorganisms at an early stage (egg or embryo) in their development so that they develop with desired characteristics.
AQA new specification-Metabolism and the liver-B9.4
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Metabolism and the liver-B9.4

(1)
Metabolism and the liver lesson created in accordance to the NEW AQA Specification (9-1). Designed for a higher ability class, although content can be adjusted to suit any ability. Includes powerpoint timers, slide animations, embedded video's and mini review. NB: If you are unable to play embedded videos please view slide notes for link. AQA spec link: 4.4.2.1 Relevant chapter: B9 Respiration. AQA Biology third edition textbook-Page 140-141 Students are required to know the following; Students should be able to explain the importance of sugars, amino acids, fatty acids and glycerol in the synthesis and breakdown of carbohydrates, proteins and lipids. Metabolism is the sum of all the reactions in a cell or the body. The energy transferred by respiration in cells is used by the organism for the continual enzyme controlled processes of metabolism that synthesise new molecules. Metabolism includes: •conversion of glucose to starch, glycogen and cellulose •the formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids • the use of glucose and nitrate ions to form amino acids which in turn are used to synthesise proteins • respiration •breakdown of excess proteins to form urea for excretion. All of these aspects are covered in more detail in the relevant specification section but are linked together here.
AQA new specification-Diseases caused by fungi and protists-B5.8
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Diseases caused by fungi and protists-B5.8

(2)
This lesson has been created in accordance to the NEW AQA Specification (9-1) for my combined/additional science class (Year 9-KS4). Includes: slide animations, embedded video, worksheet and answers have also been included within the slides. This resource is suitable for separate science students. AQA spec link: 4.3.1.4 and 4.3.1.5 Relevant chapter: B5-Communicable diseases . AQA Biology third edition textbook-Page 88-89. *The new specification requires students to know the following; Rose black spot is a fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early. It affects the growth of the plant as photosynthesis is reduced. It is spread in the environment by water or wind. Rose black spot can be treated by using fungicides and/or removing and destroying the affected leaves. The pathogens that cause malaria are protists. The malarial protist has a life cycle that includes the mosquito. Malaria causes recurrent episodes of fever and can be fatal. The spread of malaria is controlled by preventing the vectors, mosquitos, from breeding and by using mosquito nets to avoid being bitten.
AQA new specification-Material cycling-B17.2
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Material cycling-B17.2

(0)
Material cycling lesson created in accordance to the NEW AQA Specification (9-1). Designed for a higher ability class, although content can be adjusted to suit any ability. Includes powerpoint timers, slide animations, embedded video’s and mini review. NB: If you are unable to play embedded videos please view slide notes for link. AQA spec link: 4.7.2.2 Relevant chapter: B17 organising an ecosystem. AQA Biology third edition textbook-Page 278-279 Students are required to know the following; Explain the importance of the carbon and water cycles to living organisms. All materials in the living world are recycled to provide the building blocks for future organisms. The carbon cycle returns carbon from organisms to the atmosphere as carbon dioxide to be used by plants in photosynthesis. The water cycle provides fresh water for plants and animals on land before draining into the seas. Water is continuously evaporated and precipitated. Students are not expected to study the nitrogen cycle. Students should be able to explain the role of microorganisms in cycling materials through an ecosystem by returning carbon to the atmosphere as carbon dioxide and mineral ions to the soil.
AQA new specification-Pathogens and disease-B5.2
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Pathogens and disease-B5.2

(3)
Health and disease lesson created in accordance to the NEW AQA Specification (9-1) for my combined/additional science class (Year 9-KS4). Includes: slide animations, embedded video, worksheets and practice questions with answers. This resource is suitable for separate science students. AQA spec link: 4.3.1.1 Relevant chapter: B5-Communicable diseases . AQA Biology third edition textbook-Page 76-77. *The new specification requires students to know the following; Students should be able to explain how diseases caused by viruses, bacteria, protists, and fungi are spread in animals and plants. Pathogens are microorganisms that cause infectious disease. Pathogens may be viruses, bacteria, protists, or fungi. They may infect animals and can be spread by direct contact, by water, or by air. Bacteria and viruses may reproduce rapidly inside the body. Bacteria may produce poisons (toxins) that damage tissues and make us feel ill. Viruses live and reproduce inside cells, causing cell damage.
AQA new specification-Common problems of the eye-B10.6
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Common problems of the eye-B10.6

(0)
Common problems of the eye lesson created in accordance to the NEW AQA Specification (9-1). Designed for a higher ability, separate science class, although content can be adjusted to suit any ability. Includes powerpoint timers, slide animations, embedded video’s, homework worksheet, markscheme and mini review. NB: If you are unable to play embedded videos please view slide notes for link. THIS LESSON IS FOR BIOLOGY ONLY AQA spec link: 4.5.2.3 Relevant chapter: B10 The human nervous system. AQA Biology Third edition textbook-Page 156-157 Students are required to know the following; Students should be able to relate the structures of the eye to their functions. This includes: • accommodation to focus on near or distant objects Accommodation is the process of changing the shape of the lens to focus on near or distant objects. To focus on a near object: • the ciliary muscles contract • the suspensory ligaments loosen • the lens is then thicker and refracts light rays strongly. To focus on a distant object: • the ciliary muscles relax • the suspensory ligaments are pulled tight • the lens is then pulled thin and only slightly refracts light rays. Two common defects of the eyes are myopia (short sightedness) and hyperopia (long sightedness) in which rays of light do not focus on the retina. • Generally these defects are treated with spectacle lenses which refract the light rays so that they do focus on the retina. • New technologies now include hard and soft contact lenses, laser surgery to change the shape of the cornea, and a replacement lens in the eye. Students should be able to interpret ray diagrams, showing these two common defects of the eye and demonstrate how spectacle lenses correct them.
AQA new specification-Adult cell cloning B14.6
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Adult cell cloning B14.6

(0)
Adult cell cloning lesson created in accordance to the NEW AQA Specification (9-1). Designed for higher ability separates class, although content can be adjusted to suit any ability. Includes: embedded videos and timers, slide animations, practice questions with answers on slides, worksheet and an interactive quiz. NB: If you are unable to play videos a URL link can be found in the slide notes. NB: This lesson is for SEPARATE science ONLY AQA spec link: 4.6.2.5 Relevant chapter: B14 Variation and evolution. AQA Biology third edition textbook-Page 228-229. Students are required to know the following; Adult cell cloning: • The nucleus is removed from an unfertilised egg cell. • The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell. • An electric shock stimulates the egg cell to divide to form an embryo. • These embryo cells contain the same genetic information as the adult skin cell. • When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development. WS 1.3, 1.4 Explain the potential benefits and risks of cloning in agriculture and in medicine and that some people have ethical objections. There are links with this content to Advantages and disadvantages of sexual and asexual reproduction (biology only) and Selective breeding.
AQA new specification-The eye-B10.5
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-The eye-B10.5

(0)
The eye lesson created in accordance to the NEW AQA Specification (9-1). Designed for a higher ability, separate science class, although content can be adjusted to suit any ability. Includes powerpoint timers, slide animations, embedded video’s, worksheet and mini review. NB: If you are unable to play embedded videos please view slide notes for link. THIS LESSON IS FOR BIOLOGY ONLY AQA spec link: 4.5.2.3 Relevant chapter: B10 The human nervous system. AQA Biology Third edition textbook-Page 152-153 Students are required to know the following; Students should be able to relate the structures of the eye to their functions. This includes: • accommodation to focus on near or distant objects • adaptation to dim light. The eye is a sense organ containing receptors sensitive to light intensity and colour Students should be able to identify the following structures on a diagram of the eye and explain how their structure is related to their function: •retina • optic nerve • sclera • cornea • iris • ciliary muscles • suspensory ligaments.
AQA new specification-Fossils and extinction-B14.2
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Fossils and extinction-B14.2

(1)
Fossils and extinction lesson created in accordance to the NEW AQA Specification (9-1). Designed for higher ability (trilogy/combined) class, although content can be adjusted to suit any ability. Includes: embedded videos and timers, slide animations, practice questions with answers on slides, worksheet and an interactive quiz. NB: If you are unable to play videos a URL link can be found in the slide notes. AQA spec link: 4.6.3.5 Relevant chapter: B14 Genetics and evolution. AQA Biology trilogy edition textbook-Page 192-193 Students are required to know the following; Fossils are the ‘remains’ of organisms from millions of years ago, which are found in rocks. Fossils may be formed: • from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent • when parts of the organism are replaced by minerals as they decay •as preserved traces of organisms, such as footprints, burrows and rootlet traces. Many early forms of life were soft-bodied, which means that they have left few traces behind. What traces there were have been mainly destroyed by geological activity. This is why scientists cannot be certain about how life began on Earth. WS 1.3 Appreciate why the fossil record is incomplete.
AQA new specification-Infertility treatments-B11.8
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Infertility treatments-B11.8

(3)
Infertility treatments lesson created in accordance to the NEW AQA Specification (9-1) for my separates class (Year 10-KS4). Includes: slide animations, embedded video, worksheet and practice questions with mark scheme. This resource is suitable for combined science students. *Note-For higher tier only* AQA spec link:5.3.6 Relevant chapter: B11.8-Infertility treatments . AQA Biology third edition textbook-Page 174-175. *The new specification requires students to know the following; Students should be able to explain the use of hormones in modern reproductive technologies to treat infertility. This includes giving FSH and LH in a ‘fertility drug’ to a woman. She may then become pregnant in the normal way. In Vitro Fertilisation (IVF) treatment: • IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs. • The eggs are collected from the mother and fertilised by sperm from the father in the laboratory. • The fertilised eggs develop into embryos. • At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb). Although fertility treatment gives a woman the chance to have a baby of her own: • it is very emotionally and physically stressful • the success rates are not high • it can lead to multiple births which are a risk to both the babies and the mother.
AQA new specification-B5 Communicable diseases-Combined/Additional science bundle
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-B5 Communicable diseases-Combined/Additional science bundle

6 Resources
This bundle only contains the content for COMBINED/ADDITIONAL science students. It includes the B5 unit-communicable diseases. All lessons have been done in accordance to the specification requirements. Videos have been embedded for ease of use, and printer friendly resources attached. Search the individual lessons for more information on the lesson content. Save 33% by purchasing this bundle :) These lessons are suitable to teach separate science but they have 4 extra topics to learn. Lesson 1-Heath and disease Lesson 2-Pathogens and disease Lesson 3-Preventing infections Lesson 4-Viral and bacterial diseases Lesson 5-Diseases caused by fungi and protist Lesson 6-Human defense responses
AQA new specification-B11 Hormonal coordination-Biology/Separate science
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-B11 Hormonal coordination-Biology/Separate science

11 Resources
This bundle only contains the content for BIOLOGY/SEPARATE science students. It includes the B11 unit-hormonal coordination. All lessons have been done in accordance to the specification requirements. Videos have been embedded for ease of use and printer friendly resources attached. I've also included the required practical resources. Search the individual lessons for more information on the lesson content. Save 35% by purchasing this bundle :) Higher tier topics are included. Total = 10 lessons Lesson 1-Principles of hormonal control Lesson 2-The control of blood glucose Lesson 3-Treating diabetes Lesson 4-The role of negative feedback (HT) Lesson 5-Human reproduction Lesson 6-Hormones and the menstrual cycle (HT) Lesson 7-The artificial control of fertility Lesson 8-Infertility treatments (HT) Lesson 9-Germination practical Lesson 10-Plant responses and using plant hormones Good luck with your lessons :)
AQA new specification-Exchanging materials-B1.10
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Exchanging materials-B1.10

(2)
Exchanging materials lesson created in accordance to the NEW AQA Specification (9-1). Designed for a higher ability separates class, although content can be adjusted to suit any ability. Includes: slide animations, practice questions with answers on slides, worksheet, and homework (with MS) AQA spec link: 4.1.3.1 Relevant chapter: B1 Cell structure and transport. AQA Biology third edition textbook-Page 22-23 Specification requires students to know the following; A single-celled organism has a relatively large surface area to volume ratio. This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism. Students should be able to calculate and compare surface area to volume ratios. Students should be able to explain the need for exchange surfaces and a transport system in multicellular organisms in terms of surface area to volume ratio. Students should be able to explain how the small intestine and lungs in mammals, gills in fish, and the roots and leaves in plants, are adapted for exchanging materials. In multicellular organisms, surfaces and organ systems are specialised for exchanging materials. This is to allow sufficient molecules to be transported into and out of cells for the organism’s needs. The effectiveness of an exchange surface is increased by: •• having a large surface area •• a membrane that is thin, to provide a short diffusion path •• (in animals) having an efficient blood supply •• (in animals, for gaseous exchange) being ventilated.
AQA new specification-Tissues, organs and transport systems in plants-B4.6 + B4.7
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Tissues, organs and transport systems in plants-B4.6 + B4.7

(0)
***Please note this is two lessons comnined into one. *** Tissues, organs and transport systems lesson created in accordance to the NEW AQA Specification (9-1). Designed for a higher ability class, although content can be adjusted to suit any ability.Includes powerpoint timers, slide animations, embedded video’s and mini review. NB: If you are unable to play embedded videos please view slide notes for link. AQA spec link: 4.2.3.1 Relevant chapter: B4 Organising animals and plants. AQA Biology combined/third edition textbook-Page 62-65 Students are required to know the following Students should be able to explain how the structures of plant tissues are related to their functions. Plant tissues include: • epidermal tissues • palisade mesophyll • spongy mesophyll •xylem and phloem •meristem tissue found at the growing tips of shoots and roots. The leaf is a plant organ. Knowledge limited to epidermis, palisade and spongy mesophyll, xylem and phloem, and guard cells surrounding stomata. Students should be able to explain how the structure of root hair cells, xylem and phloem are adapted to their functions. Root hair cells are adapted for the efficient uptake of water by osmosis, and mineral ions by active transport. Xylem tissue transports water and mineral ions from the roots to the stems and leaves. It is composed of hollow tubes strengthened by lignin adapted for the transport of water in the transpiration stream. The role of stomata and guard cells are to control gas exchange and water loss. Phloem tissue transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage. The movement of food molecules through phloem tissue is called translocation. Phloem is composed of tubes of elongated cells. Cell sap can move from one phloem cell to the next through pores in the end walls. Detailed structure of phloem tissue or the mechanism of transport is not required.
AQA new specification-Competition in animals-B16.4
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Competition in animals-B16.4

(0)
Competition in animals lesson created in accordance to the NEW AQA Specification (9-1). Designed for a higher ability class, although content can be adjusted to suit any ability. Includes powerpoint timers, slide animations, embedded video’s and mini review. NB: If you are unable to play embedded videos please view slide notes for link. AQA spec link: 4.7.1.1 Relevant chapter: B16 Adaptations, interdependence and competitions. AQA Biology third edition textbook-Page 264-265 Students are required to know the following; Students should be able to describe: • different levels of organisation in an ecosystem from individual organisms to the whole ecosystem • the importance of interdependence and competition in a community. Students should be able to, when provided with appropriate information: • suggest the factors for which organisms are competing in a given habitat • suggest how organisms are adapted to the conditions in which they live. An ecosystem is the interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment. To survive and reproduce, organisms require a supply of materials from their surroundings and from the other living organisms there.
AQA new specification-Competition in plants-B16.5
PaperfriendlyresourcesPaperfriendlyresources

AQA new specification-Competition in plants-B16.5

(0)
Competition in plants lesson created in accordance to the NEW AQA Specification (9-1). Designed for a higher ability class, although content can be adjusted to suit any ability. Includes powerpoint timers, slide animations, embedded video’s and mini review. NB: If you are unable to play embedded videos please view slide notes for link. AQA spec link: 4.7.1.1 Relevant chapter: B16 Adaptations, interdependence and competitions. AQA Biology third edition textbook-Page 266-267 Students are required to know the following; Plants in a community or habitat often compete with each other for light and space, and for water and mineral ions from the soil. Animals often compete with each other for food, mates and territory. Within a community each species depends on other species for food, shelter, pollination, seed dispersal etc. If one species is removed it can affect the whole community. This is called interdependence. A stable community is one where all the species and environmental factors are in balance so that population sizes remain fairly constant. Students should be able to extract and interpret information from charts, graphs, and tables relating to the interaction of organisms within a community.