Hormones (auxins and tropisms)
Hormones (auxins and tropisms) Plants can respond to gravity, moisture and light. These responses are called tropisms - growth movements caused by auxins or 'plant hormones'. Auxins make some parts of a plant grow faster than others; the result may be that the plant bends towards or away from the stimulus. . Etiolation When a plant is left in the dark it puts all its energy into growing up to reach the light and makes very little chlorophyll. It will become etiolated. Eventually it should reach the light and then it can start to turn green by making chlorophyll for photosynthesis. Etiolation is the result of a tropism These two plants were grown from cuttings so they are genetically identical. They are both the same age, but one has been left in a dark place. You may notice that your houseplant turns all its leaves towards the window. It does this because light coming from one side destroys the auxin in a leaf on that side. On the other side auxin makes the leaf grow faster. The result is that the leaves are turned towards the light for photosynthesis. We call this a positive phototropism. Diagram Of positive phototropism Roots grow down into the ground by a - towards gravity. The shoot from a seed underground positive geotropism can grow upwards, away from gravity, by a negative geotropism. 2. Auxins * are plant hormones. * are also known as 'chemical
Compare how light is detected by humans and plants and the significance of such detection
Compare how light is detected by humans and plants and the signifocance of such detection By Christine Cheng S.5B(5) For human, the circular muscles contract and the radial muscle relax to decrease the size of the pupil which constrict pupil in bright light, so that less light is allowed to enter the eyes. It can allow human's eyes to be over-stimulated in strong light and prevent damage of the retina. On the other hand, the circular muscle relax and radial muscle contract to increase the size of the pupil which dilate pupil, so that more light is allowed to enter the eye. It can allow human to see when limited light is provided in dim light. Besides, photoreceptors in the retina: rod cells and cone cells are significant in detecting light. Rod cells distribute in retina (except at uellow spot and blind spot). They contain a pigment called visual purple which is sensitive to light in low intensity. It shows that rod cells are important for vision in dim light. Cone cells concentrate at the yellow spot and periphery of retina. They are sensitive to light of high intensity. It shows that cone cells are important for vision in bright light. Both rod cells and cone cells are connected to several layers of nerve cells. The nerve fibres of the nerve cells form optic nerve. Once the rod cells and cone cells are stimulated by light when light rays from an object are refracted and
Write an essay about the adaptations of green plants for photosynthesis
Write an essay about the adaptations of green plants for photosynthesis Photosynthesis is the metabolic pathway by which the inorganic compounds water and carbon dioxide are converted into carbohydrates using light energy, which is absorbed by chlorophyll. Plants need to be adapted so that maximum light energy is absorbed and therefore maximum photosynthesis occurs. Plants have adapted in order to be able to survive in many different climates such as high temperatures and humid conditions. Leaves play an important part in photosynthesis, as they are the first part of the plant, which is exposed to the light energy from the sun. They have a large surface area in order to absorb maximum light energy. The waxy cuticle and the upper epidermis are both transparent so that light can pass through the leaf into the other cells, which are needed for photosynthesis. The palisade cells in the leaf are elongated so that as much light is absorbed as possible. Palisade cells have thin cell walls so that the light has a short distance to travel before it reaches the chloroplasts. They are also tightly packed together to ensure that no light energy is lost. The palisade cells and the upper epidermis contain high number of chloroplasts to ensure that maximum light has been reabsorbed. These chloroplasts are mobile within the cytoplasm this helps to ensure that maximum light is absorbed. The
'What are the differences between Hetrophic & Autotrophic nutrition'?
A Level Biology Essay 'What are the differences between Hetrophic & Autotrophic nutrition' One of the seven processes carried out by all living organisms, nutrition occurs in both plants and animals. However, the methods they both use are very different. Autotrophic nutrition is in its simplest terms is being able to feed oneself and synthesise ones own food from simpler molecules. Hetrophic nutrition however, is the opposite, unable to synthesise its own food. Immediately, one notices which of the categories each the plants and animals fall into. It is important to stress that Autotrophic nutrition lays down the building blocks of life and provides complex organic molecules for the consumption of Hetrophic organisms. Without Autotrophic nutrition, there would be no life. Autotrophic nutrition falls on two levels. Light energy used in photosynthesis and chemical energy for processes involving chemosynthesis. Essentially plants survive on the products of photosynthesis and depend upon the power of the sun to help produce these foods. There are a number of physiological functions in plants, which also help the process of photosynthesis. In order for these organisms to achieve Autotrophic nutrition, they must gather together many raw materials from its environment for photosynthesis to occur. Plants require a source of carbon dioxide and water, chlorophyll to collect
Auxins: Plant growth Hormones.
Biology Revision Notes Auxins: Plant growth Hormones Auxins are hormones and are "chemical messengers" The have many roles in plants including: . Growth of cells by cell elongation 2. Prevention of side shoot development Growth of cells The auxin in the cells makes the cells stretchy and this is called cell elongation without it the cell would just continue to multiply Auxins allow the cellulose cell walls of young plant cells to become stretchy Because the cells contain sugars and salts, they will take up water (by osmosis) and expand. Light influences the movement of Auxin within a plant i.e. the Auxin MOVES AWAY FROM THE LIGHT. This causes the pants to grow towards the light The reason that it does this is because the auxin elongates the cells on the side that it is on (the side opposite the light) and elongates the cells making the plant longer on one side so naturally the plants bends towards the light Summary * Auxin causes cell elongation and hence growth * Auxin is produced in the tip of a shoot * Auxin is a water soluble chemical which can be absorbed into agar Prevention of side shoot development The apical bud is the source of Auxin .If the bud is present it will prevent side shoot development =Apical dominance This means that it is a tall plant to out compete all other plants for light. If the bud is removed it will allow side branches to grow
Investigation to find out how light intensity effects the rate of photosynthesis
Investigation to find out how light intensity effects the rate of photosynthesis Contents * Introduction * Aim * Hypothesis * Variables * Precaution * Fair Testing * Apparatus * Method * Diagram for Method * Results * Analysis of Results and Graphs * Conclusion * Evaluation * Errors, limitations and Improvements Introduction Flowering plants, like all living organisms, need a supply of food. They need it as a source of energy in respiration and they need it as raw material for growth and repair. Animals and most micro- organisms get their food in an organic form: they eat products from other organisms (such as fruit and eggs) or, nowadays, the organic substances made in laboratories and factories. Animals and the microorganisms that do this are called consumers. Due to the flowering plants can make their own organic food from simple inorganic substances and an outside source of energy, they are called producers. Once the producers have made their food they use it in the same way as the consumers do as a source of energy and as raw material for growth and repair Photosynthesis The simple inorganic substances from which flowering plants make their food are carbon dioxide (CO2) and water (H2O). These contain no energy that a flowering plant can use an outside source of energy is needed to combine them into a compound that the plant can use as food. The source
Plant Tropism Lab
Plant Tropism Lab DESIGN Aspect 1: Problem: How do bean plants respond to a light source? When the beans are tilted at an angle, how will the stems continue to grow? Hypothesis: The beanstalks should bend toward the light source in order to capture more light, this is called phototropism. The bean stem will likely grow upright, regardless of the angle it is tilted, and this is called gravitropism. Variables: Manipulated: influence of sunlight and gravity Responding: angle of plant growth Controlled: -same room temperature/pressure -same source of light -same amount of tilt on the beans -same source of water Aspect 2: Controlling Variables: Room temperature/pressure: keep all beans in classroom indoors, beside window Light source: sunlight from window to the right of bean plants Tilt on the beans: rotate all beans on the same day and at the same angle/direction Water: distilled water from squeeze bottles is used to water plants Aspect 3: Materials: -Kentucky Wonder beans -Stringless Green beans -Kidney beans -Pencil Pod Black beans -Golden wax beans -plastic bag -distilled water squeeze bottle -paper towel -ruler -protractor Apparatus Diagram: Diagram 1.0 Procedure: . Put a piece of paper towel in each of the 5 plastic bags, staple 5 pockets into each bag. Insert a bean into each pocket, one type of bean for each bag. Wet paper towel with
The Light Dependent Reactions of Photosynthesis
Overview Living things require energy to stay alive. The main energy source for autotrophs, a group of organisms that produce their own food, achieve this by gathering natural commodities such as water and sunlight. These sources of energy are converted through a series of biochemical l processes into substances that the autotroph can use to maintain its necessary functions. The sun is the starting point for the process of photosynthesis ("photo" refers to light sunlight). The sun emits many, many different wavelengths, including X-rays, UV rays, and a spectrum of light that is visible to us. The light used by photosynthesis is the spectra of visible light. The figure above shows the spectra of light which is absorbed by a plant. The sun is sometimes thought to emit simply a white light, but sunlight is actually reflected in a spectra similar to the one shown above. Plants appear to have a green color because this green light is not absorbed as much as other colors (with different wavelengths). As a result, this light is reflected by the plant, showing its green color. Another feature of the above graph is the inclusion of several pigments in the typical autotroph. Organisms that undergo photosynthesis contain a variety of colored pigments, which are organized on membranes within chloroplasts. These pigments include Chlorophyll a, Chlorophyll b, and various carotenoids.
Biology 1 Edexcel Science Overview Revision Notes.
Grouping living things: We can group living organisms based on external characteristics (phenotype). Some characteristics are unique to a group (such as feathers) and some are common to several (backbone). Five vertebrae groups are: . Fish 2. Amphibians 3. Reptiles 4. Birds 5. Mammals Vertebrates are either cold-blooded (poikilothermic) or warm blooded (homeotherm). Fish, amphibians and reptiles are piokliotherms. Birds and mammals are homeotherms. All living things are grouped into one of five kingdoms . Animalia – multicellular; cells do not have chlorophyll or a cell wall; they feed hetrotrophycally (find food from their environment) 2. Plantae – Multicellular; cells have chlorophyll and a cellulose cell wall; they obtain food autotrophycally (make food by photosynthesis) 3. Fungi – Multicellular; cells do not have chlorophyll and are surrounded by a cell wall NOT made out of cellulose. They feed Saprophytically (on dead organic matter) 4. Protocista are unicellular but with a nucleus 5. Prokaryote – Unicellular without a distinct nucleus ________________ CLASS;ORDER;FAMILY;GENUS;SPECIES A species is a pair of two species that are able to breed together to produce fertile offspring. However, this is not always the case. Plants often produce fertile offspring and not all organisms reproduce sexually (some a-sexually) Identification, variation
The biochemical nature oflight detection and emission
The biochemical nature of light detection and emission In this essay I aim to describe the range of biochemical pathways and mechanisms used by living organisms both to detect and to emit light. I will discuss general principles employed, and illustrate the range of different biochemistry involved by the use of many specific examples. Light Detection I will discuss the mechanism and function of light detection by five groups of light detecting molecule. The biggest of these is the rhodopsin group of proteins, I will also look at the role of phytochromes, cryptochromes, flavoproteins and porphirins in light detection. Rhodopsins are found in a diverse array of organisms, all featuring a retinoid prosthetic group linked to a an apo-protein, opsin via a protonated schiff base linkage. Electrons from the schiff base lone pair occupy an extra orbital (the 'n orbital'), therefore electrons can undergo a n-p* transition as well as a p-p* transition. Retinal proteins were first discovered in 1876 by Bell, who observed a reddish pigment that bleaches on exposure to light, which he called visual purple. Most rhodopsins contain retinal as the prosthetic group, but some have one of the other chromophores as shown below. For example freshwater fish have a rhodopsin containing 3,4-didehydroretinal, which has a red shifted UV absorption band. The opsins found in all organisms
