4. When the resources exploited byan introduced species are living organisms, they can reproduce --and they may eventually evolve defense mechanisms that promote anequilibrium between predator and prey (see Pimentel, 1988). Thetopsoil, minerals, and fossil fuels exploited by human beings donot have this capacity, however. They are more like the finiteamount of sugar in a vat or the plentiful but slow-growinglichens on St. Matthew Island.
Starvation, social strife, and disease interact incomplex ways. If famine were the sole mechanism of collapse, thespecies might become extinct quite suddenly. A population thatgrows in response to abundant but finite resources, like thereindeer of St. Matthew Island, tends to exhaust these resourcescompletely. By the time individuals discover that remainingresources will not be adequate for the next generation, the nextgeneration has already been born. And in its struggle to survive,the last generation uses up every scrap, so that nothing remainsthat would sustain even a small population. But famine seldomacts alone. It is exacerbated by social strife, which interfereswith the production and delivery of food. And it weakens thenatural defenses by which organisms fight off disease.
Even though seagrasses and seaweeds look superficially similar, they are very different organisms. Seagrasses belong to a group of plants called that include grasses, lilies and palms. Like their relatives, seagrasses have leaves, roots and veins, and produce flowers and seeds. Chloroplasts in their tissues use the sun's energy to convert carbon dioxide and water into sugar and oxygen for growth through the process of photosynthesis. Veins transport nutrients and water throughout the plant, and have little air pockets called lacunae that help keep the leaves buoyant and exchange oxygen and carbon dioxide throughout the plant. Like other flowering plants, their roots can absorb nutrients. Unlike flowering plants on land, however, they lack stomata—the tiny pores on leaves that open and close to control water and gas exchange. Instead, they have a thin cuticle layer, which allows gasses and nutrients to diffuse directly into and out of the leaves from the water. The roots and rhizomes (thicker horizontal stems) of seagrasses extend into the sediment of the seafloor and are used to store and absorb nutrients, as well as anchor the plants. In contrast, seaweeds (algae) are much simpler organisms. They have no flowers or veins, and their holdfasts simply attach to the bottom and are generally not specialized to take in nutrients. Scientists are studying what genes were lost and which were regained as seagrasses evolved from algae in the sea to plants on land, and then transitioned back to the sea. The entire genome of one seagrass, the , helping us understand how these plants adapted to life in the sea, how they may respond to climate warming, and the evolution of salt tolerance in crop plants.
That is, water (H2O) plus carbon dioxide (CO2) combined in a chloroplast in the presence of light results in f sugar (C12H22O11) plus oxygen (O2). The oxygen is a by-product, or leftover. Or waste. This 'waste' oxygen, generated by countless billions of photosynthetic bacteria and archaea for millions of years, created the oxygen atmosphere that allows animals to breathe.
All of the sugar produced in the photosynthetic cells of plants and other organisms is derived from the initial chemical combining of carbon dioxide and water with sunlight.
Green plants absorb light energy using chlorophyll in their leaves. They use it to react carbon dioxide with water to make a sugar called glucose. The glucose is used in respiration, or converted into starch and stored. Oxygen is produced as a by-product.
Chemistry in photosynthesis
All organisms that perform photosynthesis use a hydrogen source & carbon dioxide to make sugar products
Redox Reactions- While in photosynthesis energy is absorbed and used to produce sugar and oxygen from water amd carbon dioxide but in respiration the sugar is broken down using oxygen releasing water and carbon dioxide.