Chapter 45
Communities are groups of populations that interact with each other Communities rely on two different things: Composition: the actual species in a community Diversity: the number of different species and the % of each species In a community, each species cares about two things: Habitat: where an organism lives. Niche: the role an organism plays in a community. Species cannot survive together if they occupy the same niche or habitat. Examples Red Fox and Barn Owl Coyotes and Badgers
Competition is when two members of a species try to utilize the same niche (light, space, nutrients, etc). Competition forces species to either evolve to increase their chances of success or die out. On the Galapagos islands, if an island accommodates only one finch species then no competition occurs. When multiple finch species live in a community on an island, competition occurs by forcing those with the best features to obtain the best food, and those with inferior features to starve or try different foods
Predation is when one organism, the predator, feeds on another organism, the prey. Predator prey relationships follow a standard 5-part cycle 1. The prey outnumbers the predators. The predator population grows because of high amounts of food. 2. The prey population reaches their carrying capacity and begin to drop 3. The predators, not realizing the food population is dwindling, overeat and over-reproduce. They reach their carrying capacity. 4. The predator population drops because of lack of food. The lack of predators, however, allows prey to make a comeback. The prey population grows. 5. The additional prey population allows the predators to support a larger population as well. The cycle repeats.
Prey are not merely at the whim of predators. They have a variety of defenses. Weapons: spines, thorns, toxins. Camouflage Warnings: calls, colors, Mimicry: pretending to be another organism with a defense, even though the organism itself has no defenses.
Symbiosis is when two species are dependent on each other for one reason or another. Parasitism is when a parasite takes over a host for it s own benefit. The parasite does not merely consume the host as a nutrient, but uses it as a habitat and a reproductive host. Examples: viruses, malaria, leeches, tapeworms
Commensalism is another symbiotic relationship; this time one organism benefits from another while the other organism is unaffected Barnacles and whales Remoras and sharks Clownfish and anemones Mutualism is a symbiotic relationship where both organisms benefit from each other Intestinal bacteria and mammals Butterflies and pollen plants
Disturbances are anything that breaks apart a community and allows for new members to join. Disturbances are important for ecological succession, which is when a series of new species move into a community. The new species may not consume the same resources as resident species, so previously over-consumed resources can rebound The first event is the disturbance. This may be a storm, a tree falling, a volcanic eruption, etc. Next the primary species returns to the disaster area. This has to be a plant or another producer. Then comes secondary succession. Species that can feed on the primary species move in. Then species that can feed on the secondary species, etc
Keystone Species are required for every food chain Like the keystone of an arch, the keystone is at the top of the chain They control aspects of the ecosystems that ensure all other animals are able to survive Keystone Species #1: Engineers Engineers mix different habitats and, thus, mix the nutrients of the habitats They modify the habitat physically or chemically The grizzly bear removes salmon from the river but eats it on land. (Nutrients travel from water to land)
Pavers allow for biodiversity in an ecosystem What is the paver in this picture?
Gatekeepers prevent any one specie from thriving too much The starfish in the Puget Sound feed on urchins, mussels, and clams Urchins mussels and clams can give birth frequently and take over an ecosystem Starfish ensure that these species do not take over ecosystems and nutrients from other, weaker organisms
Gatekeepers help control the population by eating everything in sight. These predators prevent any other specie from thriving more than others
The earth has no energy source. The sun is the primary source of energy for all life on earth. Earth needs a method of harnessing the energy. For that, we have autotrophs Autotrophs are organisms that are able to absorb and transform energy from chemical reactions or sunlight into usable energy sources They are also called producers because they are able to produce their own food and they produce food for others
Photosynthetic organisms are autotrophs that convert sunlight into carbon compounds All plants; some bacteria; algae; monera (plankton) any that contain photosynthetic pigments Chemosynthetic organisms are autotrophs that convert gasses, inorganic compounds, and other chemicals into carbon compounds for energy Nitrates, sulfates, ammonia, etc. Deep ocean, hot spring, and cave plants; algae; monera
There are only two options: autotrophs or heterotrophs (organisms that cannot form food sources on their own and must consume it) Four types of heterotrophs Herbivores: Able to digest plant or algae materials Carnivores: Able to digest animal and insect materials Omnivores: Able to digest plant and animal materials Detrivores and Scavengers: Able to digest rotten plant and animal materials, and/or able to digest waste products
Energy flows from the sun to autotrophs to heterotrophs, but with every transfer energy is lost as heat to the atmosphere. Autotrophs have the highest efficiency on the planet. Of all the energy they gain from the sun, 55% is conserved. In contrast, every other transfer of energy (plant to herbivore, herbivore to carnivore, etc) only contains 10% of the original energy If I take a stalk of wheat and turn it into bread, the amount of energy I receive from the bread is only 10% of what was present in the stalk of wheat
Imagine a single family of field mice with 100,000 total Calories of energy is eaten by a family of owls Some of that energy will be lost as waste (carbon dioxide, urine, feces) and unable to be consumed by the owls Most of that energy will be lost as heat, a natural biproduct of every metabolic function. What remains are 10,000 Calories that have been stored within the mice that will be transferred successfully to the owls for them to use to process their own metabolism
We need both matter (the molecules that make up our nutrients) and energy (the bonds that hold the molecules together) Unlike energy (which we have a constant source of thanks to the sun) we do not have a constant source of nutrients. Therefore, energy flows in a one-way direction but matter needs to be recycled over and over. All nutrients and elements are recycled, but the main four you need to worry about for this class are water, carbon, nitrogen and phosphorus
The majority of water in the world is salty, which is unusable (and potentially dangerous) to organisms. The sun s rays are able to break the salt from the water and cause water vapors to evaporate. Evaporation from plants is called transpiration The water vapor forms a cloud of fresh water, leaving the salt in the ocean. The cloud is a large reservoir of water. The formation of the cloud gives wind enough time to push water across the ocean and towards land, where it precipitates. The water is released into lakes, rivers, streams, underground aquifers back to the ocean for recycling During it s journey it can either be purified by natural chemicals and organisms, or pick up and store pollutants
Carbon is one of the most important building blocks for chemicals and compounds in the universe. Plants use carbon dioxide to power photosynthesis. Organisms use carbon for energy storage All organisms, when they die and decay, cycle carbon back into the earth. Geysers, volcanoes, hot springs all cycle carbon from the core of the earth into the biosphere
78% of our atmosphere is nitrogen. Nitrogen is needed by organisms for building proteins, and by plants and bacteria as energy sources and energy storage. Detrivores take nitrogen sources and convert them into various forms (N 2, NO 3-, NH 4+ ) Nitrification: natural conversion of ammonia (NH 3 ) to nitrites (NO 2-2 ) and nitrates (NO 3- ) by bacteria Nitrogen fixation: free nitrogen in the atmosphere is converted to nitrites and nitrates by bacteria
Phosphorus is an important component of DNA and RNA Phosphorus is in high quantities in rock and soil. Water runoff helps remove the phosphorus from the rocks and make it available to the plants and animals Detrivores also remove used phosphorus compounds from organic waste and return it to aquifers and soil. Plants, insects and ocean life reabsorb the phosphorus suspended in water. Organisms consume the plants, insects and ocean life and continue the cycle.