Simple Plants: The Algae (1962)

every time I visit a woodland pool I always enjoy watching the whirly gig Beatles but my real interest Lies Beneath the surface for here grows one of the most important groups of plants in the world to a casual Observer these rocks are covered with nothing more than a green slime but if like this research worker you go to the trouble of putting the slime under a microscope then quite a different picture will emerge you will see a multitude of microscopic plants plants like cladophora the branch and rebr anch into numerous different filaments this long tube is ionium the golden droplets are food reserves some of the filaments look somewhat like strings of beads and this is the spiral construction of SPO Jara but all these different species of algae have one thing in common like all green plants they contain chlorophyll and so they can use the sunlight to manufacture their food supply of sugars and starches from the carbon dioxide and water present in their envir environment in return they give off oxygen oxygen that is essential to the animal life of the pant including this microscopic water flea apart from oxygen algae also provide the basic food on which nearly all aquatic animals ultimately depend algae however are very simple organisms and mustn't be confused with the various seed plants that also Al grow underwater these seed plants can always be identified by their leaves stems and Roots they also have the vascular tissue shown clearly in this stained cross-section which enables fluids to pass through their bodies algae however lack this conducting tissue an algal filament is a series of of separate cells and each cell has to absorb its own water and minerals there is no direct connection between one cell and the next but not all algae are the colonial or filamentous types that we've been looking at if you should take a drop of water from the Woodland pool you would find a large variety of plants that are composed of just a single cell there are thousands of different species of unicellular algae these are datom most of them smaller than the width of a human hair reproducing themselves by cell division they often stay clustered together in groups these small organisms creatures whose whole body and being is but one simple microscopic Cell live reproduce and die in a microw world of their own these varied shapes are desmids here you can see the movement of the cell cytoplasm in the vacuo Brownian movements can be seen the activity of some unicellular algae Mak them appear more like animals than plants however the terms plant and animal are not too significant when dealing with such primitive organisms for these minute algae are the living descendants of what were probably the first green plants on Earth possibly in a harsh environment such as this the first primitive forms of life began to appear all they needed to survive were a few minerals dissolved from the rocks and the carbon dioxide and water used in photosynthesis the ancestors of the first green plants the blue green algae are so simple in construction that their chlorophyll is not contained in small packages or chloroplasts but diffused throughout each cell in time plants evolved that had definite chloroplasts and also whip-like flagella that could propel them through the water the algae had attained Mobility then during the gradual process of evolution organisms appeared with both plant and animal characteristics one of the most striking examples is ugino they are plants in that they contain chlorophyll but if deprived of sunlight they can still sustain themselves by absorbing dissolved organic matter other animal characteristics are a flexible body wall Cella and a red ice spot this I spot is sensitive to light and guides them to areas suitable for photosyn synthesis this relative of the ugina carries the development a stage further they completely lack chlorophyll and exist solely on organic matter including bacteria at about the same time that this alga evolved other unicellular algae developed into colonies this might have come about because the daughter cells failed to separate after cell division this is volog a colonial structure of numerous individuals in this damaged Colony you can clearly see its spherical shape with volvox we have the beginning of cell specialization for some of the cells assume specific functions this group will specialized for the process of sexual reproduction during the course of time some freshwater algae must have gradually invaded the land washed up on the rocky shores of ancient Lakes but their simple yet efficient structure ensured their Survival on The Damp rocks later lyans appeared lyans are a combination of algae and fungi living together in this Cooperative Enterprise the algae supply the food while the fungus provides shelter and retains a water supply in one form or another the algae have survived for a thousand million years in late summer they reproduce so rapidly that an alal Bloom often covers the surface surface of the water their methods of reproduction also reflect an evolutionary pattern here camid amonous is reproducing asexually by the process of cell division the parent cell simply separates into two new cells a slightly more advanced type of asexual reproduction takes place in an alga like ulx motile spores are released from the plant body each of these spores will soon develop into independent plants the last stage in the evolution of sex can be seen in ionium an egg is formed in one of the cells of the filament sperm generated from other cells then fertilizes the egg this method of sexual reproduction is characteristic of all the more advanced plants and animals including ourselves an interesting variation of the reproductive process sometimes occurs in Sparro Jara two parent plants line up with one another and Carry On A Primitive form of sexual Union called conjugation a small knob grows out from each cell and join up with the knob that is protuding from the cell of the other filament then the tips of the knobs dissolve and form a passageway between the two cells through this passage the content of one cell flows into the other and the two masses of protoplasm unite to form a fertile zygote through their long and successful Evolution the algae have adapted to all types of moist environment they grow on the bark of trees they even live inside the bodies of flat worms apart from giving the worms their dark green coloring they also guarantee a food supply for the algae act as a built-in vegetable garden algae can also be found in the neighborhood of Hot Springs their presence helps to form beautifully colored mineral deposits on the Rocks high in the mountains others spend their whole life on the surface of the snow here they live and Thrive surrounded by a layer of icy water the algae however are not just confined to the land and to fresh water water for in the oceans grow the seaweeds in the open sea there is the sarasam weed kept afloat by its small air bladders but most seaweeds grow in the shallow tidal Zone and each one has an entirely different appearance from its fellows many different varieties of seaweeds will grow in the same environment and they differ in pigmentation Browns greens Reds this coloration is important for at low tide they lie Exposed on the Rocks but when the tide comes in some will live at depths where not much sunlight can penetrate however they are still able to photosynthesize for the brown and red pigmentation helps them to absorb what little sunlight is available there is little comparison here with the Primitive single celled algae these plants are not only large but extremely complex in their organization the seaweeds anchor themselves to the rocks by means of hold fasts these are not Roots but they do act to attach these free floating plants to a solid substrate the base of the plant develops finger-like projections that grow into the cracks and crevices securing the plant firmly to the Rock holding it fast against the coming and going of the time some seaweeds such as the kelp are extremely large and grow in profusion off the Pacific coast at one time they were used extensively for both humans and livestock as a source of iodine and potassium in the orient more than a 100 different seaweeds are still widely used as part of the normal vegetable diet although we are not all aware of it extracts from seaweeds are also used in the manufacturer of some popular North American food stuffs sodium alginate is a common additive to dairy products also Beauty preparations often depend for their smoothness on the ulfi extracted from seaweed but the sea is also the home of microscopic algae very similar to those found in ponds and rivers the dinoflagellate is a typical example at certain times of the year algae similar to this one create what is known as the red tide the water is poisoned by chemicals that are released from the dulet this poison is fatal to fish but by far the most important Marine algae are the datom impregnated with silica their cell walls are transparent and don't Decay when the diet arm dies these tiny organisms literally live in Glass Houses the many varieties of marine diatoms are the primary food source of the sea for they are the basic food of the Zoop Plankton which animals in turn feed the fish here in the intestine you can see the thousands of diams that are in the process of being digested these single cell plants also manufacture vast quantities of oxygen always fairly close to the surface to take advantage of the sunlight they produce over half the world's supply of oxygen from their microscopic bodies the algae are simple plants single cells that are often found strung together in Chains they were probably the first plants on Earth but are now found almost everywhere even in the mountain snows they grow on the outside of trees and the inside of some worms some are large and anchored to the Rock others are microscopic and extremely mobile they are the primary food source of aquatic animals and they provide the world with the bulk of its oxygen it is true that algae are simple plants but I think you will agree with me that they are also indispensable to the World As We Know It