Demonstrate understanding of biological ideas relating to the life cycle of flowering plants
Introduction to the topic
This standard is about the life cycles of flowering plants. Flowers are the plant's reproductive structures. Angiosperms are types of plants that bear fruits and flowers. Flowers are usually both male and female, and are brightly colored to attract insects/birds or animals to help them carry pollen used for sexual reproduction. Not all flowers are colourful, though. These flowers usually use the wind for pollination.
Mrs C Gren is often used to think about living organisms. Have a look at the following table and compare plants to animals.
Sexual vs. Asexual reproduction - General
Before we start on plants lets think about sexual and asexual reproduction in organisms.
Asexual and sexual reproduction of flowering plants (including dispersal)
In plants this occurs when the pollen from an anther is transferred to the stigma. Plants can fertilize themselves: called self-fertilization. Self-fertilization occurs when the pollen from an anther fertilizes the eggs on the same flower. Cross-fertilization occurs when the pollen is transferred to the stigma of an entirely different plant.
· Sexual reproduction involved flowering plants (two parents). They use meiosis to produce pollen and ova, which during fertilisation combine to form a seed.
· Sexual reproduction in plants involves pollen being transferred (pollination) onto a stigma and subsequent fertilisation. In asexual reproduction there is no pollen transfer and therefore no fertilisation.
When the ovules are fertilized, they will develop into seeds. The petals of the flower fall off leaving only the ovary behind, which will develop into a fruit. There are many different kinds of fruits, including apples and oranges and peaches. A fruit is any structure that encloses and protects a seed, so fruits are also "helicopters" and acorns, and bean pods. When you eat a fruit, you are actually eating the ovary of the flower.
A plant produced by sexual reproduction has a different genetic makeup from its parent plants.
Sexual reproduction begins with the production of ﬂowers by the adult plant. (male gametes) forms
by meiosis in the anther of the ﬂower. female gametes) form in the ovary
Pollination: The transfer of pollen from the anthers of a flower to the stigma of the same flower or of another flower. Pollination is needed for fertilization: the fusion of nuclei from the pollen grain with nuclei in the ovule. Fertilization allows the flower to develop seeds.
Some flowers will develop seeds as a result of self-pollination, when pollen and pistil are from the same plant, often (but not always) from the same flower. Other plants require cross-pollination: pollen and pistil must be from different plants.
Description of insect-pollinated features:
· colourful petals
· scent and nectar
· anthers and stigma located inside flower
· sticky pollen
Description of wind-pollinated features:
· anthers and stigma dangle outside flower
· large anthers and stigma
· anthers produce large amounts of pollen
· smooth, light pollen
Explanation of how features enable insect-pollination:
· colourful petals attract insects, which have colour vision
· nectar attracts insects to the flower to feed
· the sticky pollen attaches to the insect so it can be transferred
Explanation of how features enable wind-pollination:
· anthers dangle outside flower to that pollen can be released into the wind
· the stigma is large to increase the chance that it will catch passing pollen
· the pollen is light so that the wind is easily able to carry it
Features that can be compared/ contrasted:
· physical characteristics of flowers (colour, scent, size and smell)
· relative size of sex organs
· location of sex organs
· volume of pollen produced
· nature of pollen produced (surface and size)
Eg, Wind pollinated plants produce considerably more pollen than insect pollinated plants. A large amount of pollen is lost in the wind and does not reach the stigma of a flower. Equally the pollen must be light so that the wind is able to carry it. Insect pollinated plants are able to produce less pollen, as less is lost by the action of insects carrying it from one flower to the next. The pollen is sticky so that it is able to adhere to the insect for transportation.
The Perfect Flower (From Sepals to Ovules)
This is based on the perfect flower, of course all flowers are different. Let's start with the outside of the flower. The first things you see are probably its Sepals and Petals.
The Sepals form a ring of small leaf-like sections around the base of the flower. They are usually green and their job is to protect and support the flower.
The bright-colored Petals are there to attract the birds and insects who will do the important work of pollination (we'll tell you more about pollination in a minute). The Petals often smell good, too. (Some flowers depend on the wind for pollination, so their Petals are less colorful & fragrant since they don't need to attract pollinators).
The Petals form the plant's Corolla, while the Sepals form its Calyx.
Now let's peel back the Petals and look inside the Corolla.
What do you see?
First, you'll probably see some slender stalks with little grain-like things at the ends of them. The stalks are Filaments and the little things on the ends of them are Anthers. The Anther and the Filament are the male reproductive organs of the flower. Together, they are called the Stamen.
The plant's male sex cells, a powdery substance called Pollen, are formed inside the Anthers.
What else will you see inside the flower?
Well, deep in the center of the Corolla, you will see the plant's female reproductive organs. Each of these organs is called a Carpel -- and all the Carpels together are called the Pistil.
Each Carpel consists of a Stigma, a Style and an Ovary.
The Ovary is located at the base of the flower -- and this where the plant's female sex cells (called Ovules) are produced. The Style is a tube on top of the Ovary and the Stigma is the top part of the Style. The Stigma is where Pollen sticks during fertilization.
Obviously, for fertilization to take place, Pollen from the male part of a plant -- the Stamen -- must reach the Ovule deep inside the female part of a plant, the Carpel (Pistil).
It’s the plant equivalent of human sperm fertilizing a human egg. In plants, the process is called pollination.
The most important function of the leaf is to make food for the plant. The two main parts of a leaf are the leaf stalk, called the petiole, and the flat leaf blade. Inside the blade you can see a pattern of leaf veins. The veins carry food and water.
Asexual reproduction produces genetically identical offspring because there is no fertilisation. Sexual reproduction produces genetically unique offspring as a result of meiosis and fertilisation.
· Potato plants reproduce asexually using stem tubers or tubers.
· Strawberry plants reproduce asexually by producing horizontal stems called runners.
· Garlic plants reproduce asexually by producing bulbs.
· Ginger plants reproduce asexually by producing swollen horizontal underground stems called rhizomes.
· Dahlia plants reproduce asexually by producing swollen root tubers.
· Gladiolus plants reproduce asexually by producing stacks of stem bases called corms. Lilac plants can reproduce asexually by producing adventitious shoots from lateral stems that touch the soil. This method is called layering.
Asexual reproduction is also called vegetative reproduction in some NCEA questions. It involves production of new plants without the making of seeds or growth from seeds. A plant produced by asexual reproduction has the same genetic makeup as the parent plant (clone). Asexual reproduction is fast and does not require a plant to use energy to make ﬂowers, pollen and fruits which is more efficient but they do lack variation which can be a bad thing if disease hits. A large number of offspring that grow close to the parent plant are produced. Many plants that reproduce asexually also reproduce sexually at a different time of the year.
eg. · A [strawberry] plant reproduces asexually by producing [runners]. These grow by mitosis from existing tissue in the plant (single parent).
Meiosis gives rise to variation. This is an important part of sexual reproduction. The variation produced is inherited, which means that evolution can take place as a result of the natural selection of certain variants to suit a changing environment. The way that meiosis gives rise to variation is by recombining genes from chromosomes in new ways. When the number of chromosomes is halved, there is some randomness in the way parts of chromosomes are selected to go into the gametes.
Germination and growth (including development such as flowering, primary and secondary growth and photosynthesis).
The growing parts of plants are actively dividing by mitosis to make new cells and tissues. These tissues elongate and specialise. However, in root tips the division and elongation of cells results in the root growing downwards (positive geotropism) towards a source of water, while in the shoot tip the division and elongation of cells the shoot tip to grow towards the light (positive phototropism) necessary for photosynthesis.Once the new cells are produced they elongate and become bigger, and then differentiate into the specialised cells and tissues required by the plant. This process occurs in both root and shoot tips. In root tips, however, the cells may become, for example, root hair cells for increased water absorption or root cap cells that secrete a protective slime to ease the passage of the root tip through the soil as it grows. In shoots, the cells may differentiate into, for example leaf epidermal cells that develop a waxy cuticle for water conservation, or leaf palisade cells with many chloroplasts for photosynthesis.
Biological ideas relating to the life cycle of flowering plants will be selected from
related life processes
An excellent interactive workshop can be found here
Sunlight plays a much larger role in our lives than we may expect: all the food we eat and all the fossil fuel we use is a product of photosynthesis.
This process of photosynthesis converts light energy to chemical energy that can be used by living things. Photosynthesis is carried out in the leaves of plants and by algae (microscopic plants in water). These organisms convert CO2 (carbon dioxide) and water (H2O) to sugars (eg glucose C6H12O6) and oxygen (O2) in a reaction using light energy absorbed by the green pigment chlorophyll.
Chlorophyll – while this is the major pigment used in photosynthesis, there are others, e.g. in those plants that have red leaves (eg bougainvillea) or brown (bull kelp).
Sugars – while photosynthesis makes glucose, this is not the only sugar involved. This simple sugar is quickly converted to the complex sugar starch for storage (eg in leaves, fruit, roots). When energy is needed, eg by growing areas of the plant, it is converted back to glucose and transported in the sticky sap to those needy areas. In strong light some of the absorbed light energy is even converted to heat.
Gases – for this process, carbon dioxide must enter the leaf and oxygen exit. So there are tiny holes, called stomata, all over the surface of the leaf, although most are on the underside. These stomata can open or close at different times of the day. Some plants living in desert climates, such as cacti, keep their stomata closed during the day to minimize evaporation. In ideal growing conditions, sugar production is limited mostly by the amount of CO2 available (eg in a market garden, where plants are usually given plenty of nutrients and water). So, if the amount of carbon dioxide can be increased, plants will grow faster and bigger.
Light energy is cheap, clean, and inexhaustible. We already have developed solar cells to collect light energy and convert it to electricity. With limited supplies of fossil fuel and increasing concern about CO2 emissions, further development of technologies that make use of solar energy is inevitable. For example: -
- Biomedical Field - use of synthetic pigments in tumor detection (as they accumulate in cancer tumours and are fluorescent, they are easily detectable)
- Biotechnology - photosynthetic organisms are likely to play an increasing role in production of enzymes, pharmaceuticals which are currently being made by GMO’s (yeast and bacteria mainly). Without the need to add food production costs are lower.
- Bioremediation - the clean-up of pollutants in the soil or water by biological means eg cleaning up oil spills, removing nitrates from drinking water
- Making Fuels -Use have these organisms use solar energy to produce clean-burning fuels eg hydrogen or methane
Photosynthesis is a process by which light energy is converted into chemical energy.This process consists of a series of chemical reactions that require carbon dioxide (CO2) and water (H2O) and store chemical energy in the form of sugar. Light energy from light drives the reactions. Oxygen (O2) is a byproduct of photosynthesis and is released into the atmosphere. The following equation summarizes photosynthesis:
6 CO2 + 6 H2O → 6(CH2O) + 6 O2
A great starter animation here
Some excellent notes on Photosynthesis. Photosynthesis in detail
Now have a look at the following animation.
The important parts of the plant and how they relate to photosynthesis.
· the overall functioning of the plant processes
· products or outcomes of the plant processes (including raw materials and requirements)
· the effect of environmental factors, such as light intensity, temperature, wind, moisture and oxygen, on the selected plant processes.