2d: consumers no real effect on producers & oxygen - need decomposers.
Y axis: Green Algae not to 600?, dissolved oxygen not to 8, mercury not to 8.
X axis: should not start at 1.
Graphs: graphing/classic chartgo hohli
P in the water:
A biologist growing diatoms (a type of phytoplankton) in a tank of pond water discovers that adding silicon causes the diatom population to grow and the dissolved oxygen level to decrease. Based on your experiments, which statement best explains her discovery?
Silicon is a limiting nutrient for diatoms, and decomposition of dead diatoms depletes the dissolved oxygen in the water. Diatoms require silicon and oxygen for survival. When silicon is added, the diatom population grows and oxygen is used up. Silicon causes the water to become anoxic.
DO or Die: Phytoplankton, Zooplankton, then trout
Imagine two species of trout in a deep lake; one lives at the surface and the other lives at the bottom. Based on your experiments, which statement best explains why trout at the bottom of the lake would be more likely to die during an algal bloom than trout near the surface?
When wind mixes oxygen into the surface of the lake, trout at the surface are less likely to die from lack of oxygen. Nutrients enter the lake from the surface, so trout living at the surface can access more nutrients and have a better chance of survival. When wind mixes oxygen into the surface of the lake, trout at the surface are less likely to die from lack of oxygen. Fish at the bottom of the lake don?t have access to algae at the top and are therefore more likely to starve.
Toxins:
The graph below shows the average concentration of a toxin, "Compound X" detected in samples of individuals in an aquatic food chain near where the toxin was detected. Based on your experiments, which statement below is supported by the data in the graph?
Without knowing how long Compound X has been in the system, it cannot be determined whether Compound X biomagnifies. Compound X biomagnifies, because the concentration in Species A is greater than in each of the other species. Compound X does not biomagnify, because it is found in the lowest concentration in tertiary consumers and in the greatest concentration in primary producers.
Mystery Lake: add P and N
Green Algae: With more than 7,000 species growing in a variety of habitats, green algae are the most diverse group of algae, a group of photosynthetic, aquatic, plant-like organisms that do not have true roots, stems, leaves or vascular tissue and have simple reproductive structures. Distributed worldwide in the sea, in freshwater, and in moist situations on land, some algae are microscopic while some species of marine seaweeds can exceed 50m (about 164 ft) in length. Given their name, you might expect all green algae to be bright green (and most are). However, green algae utilize a diversity of pigments in addition to chlorophyll, which appears green, and thus there are green algae species with colors ranging from almost yellow to a brownish-green. Green algae growth is a natural, healthy part of a lake ecosystem, but the addition of nitrogen and phosphorus from fertilizers and other human pollutants can cause rapid, excessive growth. Moreover, as the plants die and turn to sediment that sinks, the lake bottom starts to rise. This process leads to progressively shallower lakes and can even result in some bodies of water drying out completely. In some parts of the world, species of green algae are cultivated or "farmed" for a variety of purposes. Organic beta-carotene is produced by the green algae Dunaliella salina and utilized for its medicinal properties in the prevention of some cancers, while many other species are grown for use in aquariums, which has led to the spread of several invasive species.
Cyanobacteria: Cyanobacteria are found in almost every conceivable environment, from oceans to fresh water to damp soil and temporarily moistened rocks in deserts; some even live in the fur of sloths, providing the animal with camouflage. Also known as blue-green algae or blue-green bacteria, cyanobacteria are true bacteria with a simple prokaryotic cell structure. They lack the membrane-enclosed organelles like nuclei and mitochondria, which are familiar structures in eukaryotic cells. Indeed, chloroplasts, the organelles responsible for conducting photosynthesis in green algae and higher plants, are believed to have originated from cyanobacteria through endosymbiosis, the process by which a bacterium is engulfed by another free-living organism and incorporated as a symbiotic organelle in the host cell. Many species of cyanobacteria are capable of nitrogen fixation (the conversion of N2 gas into ammonia, a form of N that can be used by plants and bacteria), while green algae, the other phytoplankton in lake ecosystems, are not. These species are reliant on "fixed" forms of nitrogen like ammonia and nitrate to fuel their growth. As a result, while green algae typically out-compete cyanobacteria, this is not generally the case in lakes that are nitrogen-limited where nitrogen-fixing cyanobacteria have a competitive advantage. Although usually present in low numbers in lakes, cyanobacteria can become very abundant in warm, shallow, undisturbed surface water. When this occurs, they can form blooms, producing smelly floating scums on the surface. Cyanobacteria can produce toxins called microcystins, rendering water unsafe for consumption. This tiny organism makes a huge contribution to global aquatic ecology. In 1986, Cyanobacterium prochlorococcus was found to account for more than half of the photosynthesis of the open ocean and Cyanobacterium synechocystis serves as an important model organism for researchers as it was the first photosynthetic organism whose genome was completely sequenced.
Zooplankton
Daphnia: Daphnia are a group of organisms known as water fleas, aptly named for their general flea-like appearance and jerky swimming motions, resembling that of the commonly known flea. They are, however, tiny crustaceans generally only about 0.2 - 3.0 mm long. Primarily found in freshwater, in the vegetation in lakes and ponds, Daphnia are often the most abundant organism in a body of water. They live as plankton in the open water of lakes, occupying the upper portion of the water column near the algae-rich surface water. In order to avoid predators, Daphnia have developed a vertical migration in the water column, moving towards lower depth during the day and coming toward the surface to eat at night. As herbivores and detritivores, feeding on phytoplankton as well as bacteria and decaying organic matter, Daphnia are well adapted to live in algal blooms, a good source of protein and carbohydrates. Daphnia therefore benefit polluted aquatic environments. Because they are so common, Daphnia are an important link in food chains of many inland water bodies, serving as a resource for numerous predators such as sticklebacks, minnows, the fry of larger fish, and larval amphibians. Daphnia exhibit both sexual and asexual reproduction. Under optimum conditions, females tend to produce eggs asexually (called 'parthenogenesis'), and such asexual populations can grow rapidly. Under more stressful conditions, males are produced and sexual reproduction becomes more common. As a result, Daphnia are frequently used in studies addressing the evolutionary value of producing males.
Bosmina: A filter feeder in the order Cladocera, Bosmina vary in size from 0.4-0.6mm. Females typically outnumber males in a population. Like Daphnia, Bosmina can reproduce via parthenogenesis, an asexual form of reproduction where growth and development of embryos occur without fertilization by a male. Asexual reproduction is initiated by favorable environmental conditions. Although typically smaller than Daphnia and often outcompeted by the larger crustacean, Bosmina are able to successfully compete for food under some conditions because they feed differently. Daphnia are a more-or-less stationary and generalized filter feeder that feeds broadly on all the food encountered that is small enough to eat. In contrast, Bosmina are active swimmers that can feed selectively but efficiently on smaller particles, in addition to adopting a more passive filter-feeding approach. Found worldwide in lakes and ponds, Bosmina play an important role in aquatic food webs through their consumption and processing of phytoplankton, serving as a resource for consumers, including many fish species.
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