Abiotic factors (environmental factors)According to biology dictionary, abiotic factors are non-living factors in the ecosystem. These factors do affect the living things in it, but they are not living themselves. In this context, we will focus mainly on light, temperature, atmospheric pressure, salinity, humidity, pH and wind. Temperature This is the hotness or coldness of an area or habitat. It directly affects the distribution and productivity (yield) of populations and communities. Most organisms are found in areas where temperature is moderate. However, certain plants and animals have adaptations that enable them to live in areas where temperatures are in the extremes such as the hot deserts and the cold Polar Regions. Temperatures not only influence distribution of organisms but also determine the activities of animals. High temperatures usually accelerates the rates of photosynthesis, transpiration, evaporation and the decomposition and recycling of organic matter in the ecosystem. Light Light is required by green plants for photosynthesis. Light intensity, duration and quality affect organisms in one way or another. Atmospheric Pressure This is the force per unit area of atmospheric air that is exerted on organisms at different altitudes. Growth of plants and activity of animals is affected by atmospheric pressure e.g., rate of transpiration in plants and breathing in animals. Salinity This is the salt content of soil or water. Animals and plants living in saline conditions have special adaptations. Humidity Humidity describes the amount of moisture (water vapour) in the air. It affects the rate of transpiration in plants and evaporation in animals. pH pH Is the measure of acidity or alkalinity of soil solution or water, it is very important to organisms living in water and soil. Most organisms prefer a neutral pH. Wind: Wind is moving air currents and it influences the dispersion of certain plants by effecting the dispersal of spores, seeds and fruits. Air currents also modify the temperature and humidity of the surroundings. Topography: These are surface features of a place. The topographical factors considered include altitudes, gradient (slope), depressions and hills, all these characteristics affect the distribution of organisms in an area e.g. the leeward and windward sides of a hill. Biotic factorsThese are living components of an ecosystem. These factors affect the ecosystem through enhancing Inter-relationships between Organisms The relationships between organisms in a given ecosystem is primarily a feeding one. Organisms in a particular habitat have different feeding levels referred to as trophic levels. There are two main trophic levels: Producers: These organisms that occupy the first trophic level, they manufacture their own food hence are autotrophic. Consumers: These are the organisms that feed on organic substances manufactured by green plants, they occupy different trophic levels as follows: Primary consumers: These are herbivores and feed on green plants. Secondary consumers: These are carnivores and feed on flesh. First order carnivores feed on herbivores while second order carnivores feed on other carnivores, i.e., tertiary consumers. Omnivores: These are animals that feed on both plant and animal material. They can be primary, secondary or tertiary consumers. Competition between themselves for survival this describes the situation where two or more organisms in the same habitat require or depend on the same resources. Organisms in an ecosystem compete for resources like food, space, light, water and mineral nutrients. Competition takes place when the environmental resource is not adequate for all.
Predation is a relationship whereby one animal (the predator) feeds on another (the prey). Saprophytism
Nitrogen cycle
Questions on Topic 1. The flow chart below shows a food web in a terrestrial ecosystem.
2. The food web represents a feeding relationship in an ecosystem.
3. State four abiotic factors in an ecosystem. 4.
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​Concept of reproduction
​The process by which mature individuals produce offspring is called reproduction. Reproduction is a characteristic of all living organisms and prevents extinction of a species.
There are two types of reproduction:
​Importance of reproduction
​The main importance to reproduction is to give rise to young ones of same ensuring continuity of the group.
​Chromosomes, mitosis and meiosis (mention gamete formation)
Cell Division
Cell division starts with division of nucleus. In the nucleus are a number of thread-like structures called chromosomes, which occur in pairs known as homologous chromosomes. Each chromosome contains-genes that determine the characteristics of an organism. The cells in each organism contains a specific number of chromosomes. There are two types of cell division:
a) Mitosis This takes place in all body cells of an organism to bring about increase in number of cells, resulting in growth and repair. The number of chromosomes in daughter cells remain the same as that in the mother cell. Mitosis is divided into five main stages:
b) Meiosis
This type of cell division takes place in reproductive organs (gonads) to produce gametes. The number of chromosomes in the gamete is half that in the mother cell. Meiosis involves two divisions of the parental cell resulting into four daughter cells. The mother cell has the diploid number of chromosomes. The four cells (gametes) have half the number of chromosomes (haploid) that the mother cell had, in the first meiotic division there is a reduction in the chromosome number because homologous chromosomes and not chromatids separate. Homologue pairs separate during a first round of cell division, called meiosis I. Sister chromatids separate during a second round, called meiosis II. Since cell division occurs twice during meiosis, one starting cell can produce four gametes (eggs or sperm). In each round of division, cells go through four stages: prophase, metaphase, anaphase, and telophase. [additional information by the Khan Academy] Meiosis I (First Meiotic division) Before entering meiosis I, a cell must first go through interphase. As in mitosis the cell prepares for division, this involves replication of chromosomes, organelles and buildup of energy to be used during the meiotic division.
Usually the two daughter cells go into a short resting stage (interphase) but sometimes the chromosomes remain condensed and the daughter cells go straight into metaphase of second meiotic division. The second meiotic division takes place just like mitosis.
​Asexual reproduction
Asexual reproduction is the formation of offspring from a single parent, the offspring are identical to the parent.
Types of asexual reproduction.
Binary fission in amoeba
​This involves the division of the parent organism into two daughter cells, the nucleus first divides into two and then the cytoplasm separates into two portions. Binary fission also occurs in bacteria, Paramecium, Trypanosoma and Euglena.
​Spore formation/reproduction in mucor / Rhizopus
Rhizopus is a saprophytic fungus which grows on various substrate such as bread, rotting fruits or other decaying organic matter. The vegetative body is called mycelium which has many branched threads called hyphae. Horizontal hyphae are called stolons, vertical hyphae are called sporangiophore.
The tips of sporangiophore become swollen to form sporangia, the spore bearing structure, each sporangium contains many spores, as it matures and ripens, it turns black in colour. When fully mature the sporangium wall burst and release spores which are dispersed by wind or insects. When spores land on moist substratum, they germinate and grow into a new Rhizopus and start another generation. Spore formation in ferns The fern plant is called a sporophyte, on the lower side of the mature leaves are sari (Singular: sorus) which bear spores. ​Budding in yeast
​Budding involves the formation of a protrusion called a bud from the body of the organism, the bud separates from the parent cell, in yeast budding goes on so fast and the first bud starts to form another bud before the separation. A short chain or mass of cells is formed.
WHAT IS ECOLOGY?Introduction Ecology, also called ‘bioecology’, ‘bionomics’, or ‘environmental biology’ is the scientific study of interactions among organisms and between organisms and their environment. "The word ecology was coined by the German zoologist Ernst Haeckel, who applied the term oekologie to the “relation of the animal both to its organic as well as its inorganic environment.” The word comes from the Greek oikos, meaning “household,” “home,” or “place to live.”" Thus, ecology deals with the organism and its environment. [Source: britannica.com] Organisms are affected by their environment, and they in turn affect the environment. Green plants manufacture food by photosynthesis which other organisms obtain directly or indirectly. Growth of plants is mainly affected by environmental factors such as soil and climatic factors, on the other hand, organisms modify the environment through various activities. This interrelationship comprises the study of ecology, which is important in several fields of study such as agriculture and environmental studies. Concepts of EcologyEcosystem The community and the abiotic or non-living environment together make up an ecosystem or ecological system. In this system energy flow is clearly defined from producers to consumers and nutrient cycling takes place in paths that links all the organisms and the non-living environment. Habitat This is the place or "home" that an organism lives or is found, e.g., forest or grassland. Niche A niche is the functional unit in the habitat which includes not only the specific place in which an organism lives but also how the organism functions. To avoid or reduce competition, organisms are separated or segregated by their niches, for example, different species of birds make their nest on one tree, some at tips of terminal branches, and others feed on leaves, some on flowers and yet others on fruits of the same tree, i.e., food niche. Yet others feed on same food, e.g., worms in the same place but at different times - time niche. Population The term population refers to the total number of individuals of a species living in a given area at a particular time. Density Density is used in relation to population to refer to the number of individuals of a population found in a unit area. Community This is the term used to describe all the organisms living together in an area. During the development of an ecosystem, the species composition of a community changes progressively through stages. Finally a steady state is reached and this is described as the climax community. This development of an ecosystem is termed succession. Each stage in development of an ecosystem is a sere. (A seral community (or sere) is an intermediate stage found in ecological succession in an ecosystem advancing towards its climax community. In many cases more than one seral stage evolves until climax conditions are attained.)[Source: wikipedia.org]. Succession is primary when it starts with bare ground, and secondary when it starts in a previously inhabited area e.g. after clearing a forest. Biomass This is the mass of all the organisms in a given area, ideally, it is the dry mass that should be compared. Dictionary.com defines biomass as; ‘the amount of living matter in a given habitat, expressed either as the weight of organisms per unit area or as the volume of organisms per unit volume of habitat.’ Carrying capacity This is the maximum sustainable density in a given area e.g. the number of herbivores a given area can support without overgrazing. Dispersion This is the distribution of individuals in the available space. Dispersion may be uniform as in maize plants in a plantation; random as in cactus plants in the savannah ecosystem or clumped together as in human population in cities. Ecology Practical Activities
Adaptions to HabitatHydrophytes
Comparison of Root nodules from fertile and poor soilsRoot nodules
Estimation of Population using Sampling Methods
Energy Flow in an EcosystemMost of the energy used in an ecosystem is derived from the sun. Solar energy is trapped by photosynthetic plants. It flows through different trophic levels and at each level energy is lost as heat to space and also through respiration. Besides animals lose energy through excretion and defecation, the amount of energy passed on as food from one trophic level to another decreases progressively. The energy in the organisms is recycled back to plants through the various nutrient or material cycles. Food ChainsA food chain is a linear relationship between producers and consumers. It represents the transfer of food energy from green plants through repeated stages of eating and being eaten. Types of Food Chain
Detritivores feed on organic wastes and dead matter derived from the grazing food chain. Many different types of organisms feed on detritus, they include fungi, protozoa, insects, mites annelids and nematodes. Food Web In a natural community, several food chains are interlinked to form a food web. Several herbivores may feed on one plant, similarly, a given herbivore may feed on different plants and may in turn be eaten by different carnivores. Decomposers These are mainly bacteria and fungi. These organisms feed on dead organic matter thereby causing decomposition and decay and releasing nutrients for plants. They form a link between the biotic and the abiotic components. Pyramid of Numbers Refers to the number of organisms in each trophic level presented in a graphic form and a pyramid shape is obtained. The length of each bar is drawn proportional to the number of organisms represented at that level. This is because an herbivore feeds on many green plants. One carnivore also feeds on many herbivores. In a forest the shape of the pyramid is not perfect, this is because very many small animals such as insects, rodents and birds feed on one tree. Pyramid of Biomass This is the mass of the producers and consumers at each trophic level drawn graphically. Population Estimation MethodsIt is important to find or estimate the sizes of the different populations in a habitat. Direct counting or head count which involves the counting of every individual, is not always applicable for all organisms. e.g., it is impossible to count directly the numbers of grasshoppers in an area. Different sampling methods are thus used; a sample acts as a representative of the whole population. . Sampling MethodsQuadrat Method A Quadrat is a square, made of wood’s metal/hard plastic. It can also be established on the ground using pegs, rope/permanent coloured ink, using metre rule or measuring tape. The size is usually one square metre (1M2), in grassland. In wooded or forest habitat it is usually larger, and can reach up to 20 m2 depending on particular species under investigation. The number of each species found within the quadrat is counted and recorded. Total number of organisms is then calculated by, finding the average quadrats and multiplying it with the total area of the whole habitat. The number of quadrats and their positions is determined by the type of vegetation studied. In a grassland, the quadrat frame can be thrown at random. In other habitats of forest, random numbers that determine the locus at which to establish a quadrat are used. Line Transect A line transect is a string or rope that is stretched along across the area in which all the plants that are touched are counted. It is tied on to a pole or tent peg. It is particularly useful where there is change of populations traversing through grassland, to woodland to forest land. This method can also be used in studying the changes in growth patterns in plants over a period of time. Belt Transect Two line transects are set parallel to each other to enclose a strip through the habitat to be studied. The width is determined by the type of habitat, i.e., grass or forest and by the nature of investigation. In grassland it can be 0.5 m or 1 m. Sometimes it can be 20 metres or more especially when counting large herbivores. The number of organisms within the belt is counted and recorded. Capture-recapture method This is used for animals such as fish, rodents, arthropods and birds. The animals are caught, marked, counted and released. For example, grasshoppers can be caught with a net and marked using permanent ink. After sometime, the same area is sampled again, i.e., the grasshoppers are caught again. The total number caught during the second catch is recorded. The number of marked ones is also recorded:
The following assumptions are made:
Density is calculated by dividing the number of organisms by the size of the area studied. Frequency: Frequency is the number of times that a species occurs in the area being studied. Percentage Cover: This is the proportion of the area covered by a particular species. For example, a given plant species may cover the whole of a given area. In this case the plant is said to have 100% cover. Dominance: This is the term used to describe a species that exerts the most effect on others. The dominance may be in terms of high frequency or high density. Adaptations of Plants to Various HabitatsOrganisms have developed structural features that enable them to live successfully in their particular habitats. Plants found beneath the canopies of trees are adapted to low light intensities by having broad leaves. Xerophytes These are plants that grow in dry habitats, i.e., in deserts and semi-deserts. They have adaptations to reduce the rate of transpiration in order to save on water consumption. Others have water storage structures. Adaptations include:
These are the ordinary land plants which grow in well-watered habitats and have no special adaptations. Stomata are found on both upper and lower leaf surfaces for efficient gaseous exchange and transpiration. However, those found in constantly wet places e.g. tropical rain forests, have features that increase transpiration. These plants are called hygrophytes. The leaves are broad to increase surface areas for transpiration and thin to ensure short distance for carbon (IV) oxide to reach photosynthetic cells and for light penetration. The stomata are raised above the epidermis to increase the rate of transpiration. They have grandular hairs or byhathodes that expel water into the saturated atmosphere. This phenomenon is called guttation. Hydrophytes (Water plants) Water plants are either submerged, emergent or floating. Submerged Plants The leaves have an epidermis with very thin walls and a delicate cuticle. They have no stomata. Water is excreted from special glands and pores at the tips. Other adaptations include the following:
Their structure is similar to that of mesophytes. The leaves are broad to increase the surface area for water loss. They have more stomata on the upper surface than on the lower surface to increase rate of water loss. Examples are Pistia sp. (water lettuce), Salvinia and Nymphea. Halophytes (Salt plants) These are plants that grow in salt marshes and on coastlines, have root cells that concentrate salts and enable them to take in water by osmosis; they also have salt glands which excrete salts. Fruits have large aerenchymatous tissues for air storage that makes them float, Some have shiny leaves to reduce water loss. The mangrove plants have roots that spread horizontally, and send some branches into the air. These aerial roots are known as breathing roots or pneumatophores. They also have lenticel-Iike openings called pneumatothodes through which gaseous exchange takes place. Effect of Pollution on Human Beings and other OrganismsPollution This is the introduction of foreign material, poisonous compounds and excess nutrients or energy to the environment in harmful proportions. Any such substance is called a pollutant. Effects and Control of causes of Pollutants in Air, Water and Soil Industrialisation and urbanisation are the main causes of pollution. As human beings exploit natural resources the delicate balance in the biosphere gets disturbed. The disturbance leads to the creation of conditions that are un-favourable to humans and other organisms. Sources of Pollutants
In most cases, chex, pical wastes from industries are discharged into water. Toxic chemicals such as mercury compounds may be ingested by organisms. Insecticides like DDT, and weedkillers eventually get into the water and contaminate it. Oil and detergents also pollute water. Excess nitrates and phosphates from sewage and fertilisers cause overgrowth of algae and bacteria in water. This is called eutrophication. As a result there is insufficient oxygen which causes the deaths of animals in the water. Air pollution: Smoke from industries and motor vehicles contains poisonous chemicals like carbon (II) oxide, carbon (IV) oxide, sulphur (IV) oxide and oxides of nitrogen. When sulphur (IV) oxide and oxides of nitrogen dissolve in rain, they fall as acid rain. Accumulation of carbon (IV) oxide in the atmosphere causes the infrared light to be confined within the atmosphere, the earth's temperature rises. This is called the greenhouse effect. Carbon particles in smoke coat the leaves of plants and hinder gaseous exchange and photosynthesis. The particles also form smog in the air. Lead compounds are from vehicle exhaust pipes. All these have negative effects on man and the environment. Soil/Land pollution: Plastics and other man-made materials are biologically non-degradable i.e they are not acted upon by micro-organisms. Scrap metal and slag from mines also pollute land. Failure to rehabilitate mines and quarries also pollute land. Effects of Pollutants to Humans and other organisms
Human diseasesThe term disease denotes any condition or disorder that disrupts the steady state of wellbeing of the body. Health is a state of physical, mental and emotional wellbeing in the internal environment of the body. Some of the causes of diseases are due to entry of pathogens and parasites. Pathogens include bacteria, viruses, protozoa and fungi. Parasites are organisms which live on or in the body of another organisms. Vectors are animals that carry the pathogen from one person to another. Most are ectoparasites that transmit the disease as they feed. Bacterial diseases - Cholera and TyphoidCholera Causative agent is a bacterium Vibrio cholerae. Transmission It is spread through water and food contaminated by human faeces containing the bacteria. The bacteria produce a powerful toxin, enterotoxin that causes inflammation of the wall of the intestine leading to:
Carriers should be identified, isolated and treated during outbreaks. Treatment
Typhoid Causative agent The term disease causative agent usually refers to the biological pathogen that causes a disease, such as a virus, parasite, fungus, or bacterium. Technically, the term can also refer to a toxin or toxic chemical that causes illness. [Source: wikipedia.org]
Protozoa - Malaria and Amoebic dysentry (Amoebiasis)Malaria
Use appropriate anti-malarial drugs. Amoebic dysentry (Amoebiasis) Causes This disease is caused by Entamoeba histolytica. The parasites live in the intestinal tract but may occasionally spread to the liver. Transmission - They are transmitted through contaminated water and food especially salads. Symptoms
Treatment of infected people with appropriate drugs. Ascaris lumbricoides and SchistosomaAscaris lumbricoides Ascaris lumbricoides lives in the intestines of a man or pig, feeding on the digested food of the host. The body of the worm is tapered at both ends. The female is longer than the male. Mode of transmission
Deworm using appropriate drugs - ant-helminthic. Schistosoma Schistosoma or bilharzia worm is a flat worm, parasitic on human beings and fresh water snails. (Biomphalaria and Bulinus). The snail act as intermediate host. Mode of Transmission Schistosomiasis also known as a bilharsiasis is caused by several species of the genus schistosoma. Schistosoma haematobium - infects the urinary system mainly the bladder. S. japonicum and S. mansoni both infect the intestines. Schistosoma haemotobium is common in East Africa where irrigation is practised and where slow moving fresh water streams harbour snails. It is spread through contamination of water by faeces and urine from infected persons. The embryo (miracidium) that hatch in water penetrates into snails of the species Biompharahia and Bulinus. Inside the snail's body, the miracidium undergoes development and multiple fission to produce rediae. The rediae are released into the water and develop to form cercariae which infect human through:
Effects on the host
Specific Objectives
By the end of the topic, the learner should be able to:
topics/subtopics outline
​Meaning and significance of respiration
Tissue respiration 1. Mitochondrion - structure and function 2. Aerobic respiration (Details of kreb's cycle not required) 3. Anaerobic respiration in plants and animals, the products and byproducts 4. Application of anaerobic respiration in industry and at home 5. Compare the energy output of aerobic and anaerobic respiration78 Practical Activities 1. Carry out experiments to investigate 2. The gas produced when food is burnt 3. The gas produced during fermentation 4. Heat production by germinating seeds ​Meaning and Significance of Respiration
​Respiration is the process by which energy is liberated from organic compounds such as glucose.
It is one of the most important characteristics of living organisms. Energy is expended (used) whenever an organism exhibits characteristics of life, such as feeding, excretion and movement. Respiration occurs all the time and if it stops, cellular activities are disrupted due to lack of energy. This may result in death e.g., if cells in brain lack oxygen that is needed for respiration for a short time, death may occur. This is because living cells need energy in order to perform the numerous activities necessary to maintain life. The energy is used in the cells and much of it is also lost as heat. In humans it is used to maintain a constant body temperature. Tissue Respiration
Mitochondrion Structure and Function
Structure
Adaptations of Mitochondrion to its Function
Aerobic Respiration
Anaerobic Respiration
​Anaerobic respiration involves breakdown of organic substances in the absence of oxygen.
It takes place in some bacteria and some fungi. Organisms which obtain energy by anaerobic respiration are referred to as anaerobes. Obligate anaerobes are those organisms which do not require oxygen at all and may even die if oxygen is present. Facultative anaerobes are those organisms which survive either in the absence or in the presence of oxygen. Such organisms tend to thrive better when oxygen is present e.g. yeast. Products of Anaerobic Respiration The products of anaerobic respiration differ according to whether the process is occurring in plants or animals. Anaerobic Respiration in Plants Glucose is broken down to an alcohol, (ethanol) and carbon (IV) oxide. The breakdown is incomplete. Ethanol is an organic compound, which can be broken down further in the presence of oxygen to provide energy, carbon (IV) oxide and water. Fermentation
​This is the term used to describe formation of ethanol and carbon (IV) oxide from grains
Yeast cells have enzymes that bring about anaerobic respiration. Lactate Fermentation This is the term given to anaerobic respiration in certain bacteria that results in formation of lactic acid Anaerobic Respiration in Animals Anaerobic respiration in animals produces lactic acid and energy.
​When human muscles are involved in very vigorous activity, oxygen cannot be delivered as rapidly as it is required.
The muscle respire anaerobically and lactic acid accumulates. A high level of lactic acid is toxic. During the period of exercise, the body builds up an oxygen debt. After vigorous activity, one has to breathe faster and deeper to take in more oxygen. Rapid breathing occurs in order to break down lactic acid into carbon (IV) oxide and water and release more energy. Oxygen debt therefore refers to the extra oxygen the body takes in after vigorous exercise. Practical Activities
To Show the Gas Produced When the Food is burned
​Comparison between Aerobic and Anaerobic Respiration
Comparison between Energy Output in Aerobic and Anaerobic Respiration
Substrates for Respiration
​Carbohydrate, mainly glucose is the main substrate inside cells.
Lipids i.e. fatty acids and glycerol are also used. Fatty acids are used when the carbohydrates are exhausted. A molecule of lipid yields much more energy than a molecule of glucose. Proteins are not normally used for respiration. However during starvation they are hydrolysed to amino acids, dearnination follows and the products enter Kreb's cycle as urea is formed. Use of body protein in respiration result to body wasting, as observed during prolonged sickness or starvation. The ratio of the amount of carbon (IV) oxide produced to the amount of oxygen used for each substrate is referred to as Respiratory Quotient (RQ) and is calculated as follows:
​Carbohydrates have a respiratory quotient of 1.0 lipids 0.7 and proteins 0.8.
Respiratory quotient value can thus give an indication of types of substrate used. Besides values higher than one indicate that some anaerobic respiration is taking place. Application of Anaerobic Respiration in Industry and at Home
Industry
respiration audio visuals
ENZYMES
AEROBIC VS ANAEROBIC RESPIRATION
LACTIC ACIDS
EXCRETION
BODY TEMPERATURE
HOMEOSTASIS
Respiration Questions
CONTENTS
SPECIFIC OBJECTIVESBy the end of the topic, the learner should be able to:
Classification II |
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Component ​
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Inspired % ​
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Expired % ​
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Oxygen
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21
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16
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Carbon dioxide
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0.03
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4
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Nitrogen
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79
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79
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Moisture
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Variable
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​Saturated
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From here, it moves into the intercellular space in the spongy mesophyll layer.
The CO2 goes into solution when it comes into contact with the cell surface and diffuses into the cytoplasm. A concentration gradient is maintained between the cytoplasm of the cells and the intercellular spaces. CO2 therefore continues to diffuse into the cells.
The oxygen produced during photosynthesis moves out of the cells and into the intercellular spaces.
From here it moves to the substomatal air chambers and eventually diffuses out of the leaf through the stomata. At night oxygen enters the cells while CO2 moves out.
These questions are good for group discussions in and out of a classroom environment they can also be used in a question and answer brainstorming sessions
PLANT CELL
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ANIMAL CELL
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Has a cell wall and a cell membrane
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Has cell membrane only
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Nucleus at periphery
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Nucleus at the center
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Have chloroplasts
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Have no chloroplasts
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Are usually large
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Are usually small
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Has a large central vacuole
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Has no vacuoles, they are small and scattered
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Are regular in shape
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Irregular in shape
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Has no centriole
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Has centrioles
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Stores starch, oils and protein
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Store glycogen and fats
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Type of tissue
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Functions
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1. Epithelial Tissue
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Covering, allowing movement of materials
Covering of internal organs, lining for body cavity. Secretion, absorption e.g. in the alimentary canal. Covering surfaces, protection e.g. the skin. Absorption e.g. in the kidney tubules. |
Thin flat cells.
Cells that are longer than they are wide. Several layers of epithelial cells (either squamous. cuboidal or columnar). Cube like cells. |
2. Muscular Tissue
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Contraction, bringing about movement of body parts.
Contract and allow movement. Cover internal organs; allow movement e.g. peristalsis. Cause contraction of the heart. |
Consists of units called myofibrils.
Are multinucleated; have transverse striations; Controlled by voluntary nervous system. Are spindle-shaped. mononucleated; Controlled by involuntary nervous system. contract rhythmically; are myogenic (ability to contract is within) |
3. Supporting Tissue
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Support the body. provide a rigid
Framework, protect soft tissue. |
Cells that produce hard materials.
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4. Blood
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Transport of materials, protection against disease.
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A complex tissue consisting of three types of cells suspended in a fluid medium (Plasma)
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5. Nerve Tissue
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Receive stimuli and transmit impulses; co-ordinate body activities
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Consists of cells called neurons which are interconnected through axons to enable transmission of impulses
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Type of Tissue
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Functions
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Characteristics
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Meristematic
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Undergo division and cause growth, e.g. increase in length and girth
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Small thin-walled cells, contain a lot of cytoplasm; found mostly at the tip of shoots and roots.
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Parenchyma
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Photosynthesis gaseous exchange; support; storage.
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Thin walled cells; vary in shape and size; many intercellular spaces.
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Collenchyma
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Strengthening
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Thickened walls; no intercellular spaces; found in cortex of stems.
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Sclerenchyma
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Strengthening
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Vary in shape; thick cell walls; are usually dead.
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Vascular
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Transport materials.
Transport of water and mineral salts. Transport of organic materials (manufactured food). |
Tubular vessels and trancheids joined end to end.
Sieve elements joined to each other through sieve pores. |
PLANTS
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ANIMALS
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​Plants are fixed in a position
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​Most animals move in search of food
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Respond slowly to stimuli
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​Respond quickly to stimuli
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​Cells have cellulose walls
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Cells have no cell walls
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Plants make their own food from materials such as carbon dioxide and water using light energy
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​Animals feed on already made food
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schemes of work
more mocks/kcse questions & answers
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Vertical Divider
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FORM 1ARRANGED ACCORDING TO TOPICS
FORM 2
FORM 3
FORM 4
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November 2023
October 2023
September 2023
March 2023
January 2023
October 2022
September 2021
June 2021
May 2021
All
CELL PHYSIOLOGY
Classification 1
CLASSIFICATION II
ECOLOGY
EVOLUTION
EXCRETION AND HOMEOSTASIS
FORM 1
FORM 2
FORM 3
FORM 4
Gaseous Exchange In Animals
GASEOUS EXCHANGE IN PLANTS AND ANIMALS
GROWTH & DEVELOPMENT
HUMAN DISEASES
INTRODUCTION TO BIOLOGY
Lipids
MEASUREMENT OF GROWTH
NUTRITION IN ANIMALS
NUTRITION IN PLANTS AND ANIMALS
PDF NOTES
PRACTICAL ACTIVITIES
REPRODUCTION IN PLANTS AND ANIMALS
RESPIRATION
THE CELL
Transport In Animals
TRANSPORT IN PLANTS AND ANIMALS
Primary Resources
College Resources
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Secondary Resources
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