IB Biology HL Exam: Option C, Ecology/Conservation Topics for Paper 3

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Zooxanthellae
These organisms are mutualistic, photosynthetic algae that are contained within coral reefs. Their role is providing glucose and amino acids to reef-building species by photosynthesis. The coral reefs provide these algae with a protected environment and a substrate that holds them in place so that photosynthesis can occur. These algae are responsible for the unique coloration of many corals, and make reefs one of the most biologically productive ecosystems.
Interspecific Interactions
Species can interact with their environments in a wide range of ways. Parasitism, commensalism, mutualism, predation, and herbivory.
Food Conservation Ratios
The quantity of dietary input in grams required to produce a certain quantity of body mass in livestock or fish.
Succession
The changes that transform ecosystems over time. Changes involve both the species making up the community and their abiotic environment. They are the result of complex interactions between community and environment. Know the difference between primary and secondary, in which primary begins with merely abiotic environment (think glacial retreat) and only organisms that can survive on rock surfaces (bacteria, lichens) are present. Secondary in which there is or was an existing ecosystem, disturbed by an outside factor.
Non-Native Species and Biological Control
The Cane Toad was introduced in Australia in 1935 to control the Cane Beetle. Unfortunately, the toad has exploded in population size because it is not preyed upon due to a toxic gland that will kill its predators. The zebra mussel is an invasive species in the North American Great Lakes region, transported there by the ballast water of cargo ships. It clogs pipes and can destroy docks and harbors as well as harming endemic species of the region.
DDT (dichlorodiphenyltrichloroethane)
Insecticide that was used widely in the mid-20th century for disease control by vectors such as insects and then as agricultural insecticide. It biomagnified in food chains, affecting the egg shells of birds and thus their populations suffered. It also could affect human health in a variety of ways and is banned in many countries who previously utilized it for control of malaria vectors.
Laysan Albatross
Marine plastic debris and macroplastic are major concerns for marine animals as they can be mistaken for food and ingested. Laysan albatross nest on the island of Midway Atoll in the North Pacific Ocean, where the North Pacific Gyre dumps large deposits of plastic waste on the beaches. The albatross consume this plastic and feed it to their chicks, resulting in significantly high mortality rates.
Captive Breeding
A method used to restore populations of endangered species. The peregrine falcon fell victim to the use of DDT, and are now the object of a successful captive breeding program that is slowly restoring their numbers.
Factors that influence population growth
Logistic growth curve is a model of population growth. Mortality factors include: senescence, predation, disease, injury, shortage of water and food, and density independent factors such as earthquakes and volcanic eruptions.
Bottom-Up & Top-Down Limiting Factors
Free-living algal blooms can disrupt coral reef communities by blocking sunlight and preventing photosynthesis in the symbiotic zooxanthellae. Coral-reef ecosystems are nutrient poor, and this represents a bottom-up limiting factor (availability of resources) to free-living algae population growth. Parrotfish that inhabit coral reefs graze on free-living algae and thus have a top-down limiting effect (keystone species prevents lower trophic levels from monopolizing critical resources).
Waterlogging
Soil can become inundated by water through flooding, irrigation or poor drainage. It hence forth becomes waterlogged. Oxygen is in very short supply in such soils and therefore decreases the available aeration and favors the process of denitrification.
Carnivorous Plants
Insectivorous plants are adapted to water-logged soils which are nitrogen-deficient. These plants must obtain nitrogen nutrients through the extracellular digestion of animals.

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