Lecture Notes for Ecology

Introduction to ecology and ecological concepts

TERMINOLOGY AND DEFINITIONS
Ecology
the study of the relationships and interactions between organisms and their physical, non-living (abiotic) environment and their biological, living (biotic) environment.
Environment
all of the elements in an organism's surroundings that can influence its behavior or survival.
Biosphere
the relatively thin layer of life that occurs near the surface of the earth and the physical-chemical environment in which it is embedded.
Biome
A major ecological community type such as grassland or desert; collection of ecosystems.
Ecosystem
the biological communities in an area and the physical environment with which it interacts; collections of communities.
Community
all of the organisms that live in a given area; sometimes a more restricted group is designated, such as the 'bird community' - all of the birds found in a given area; plant communities, animal communities, etc.; many groups of different species of organisms; collection of populations.
Land resource area
geographic region within a community, typified by characteristic geographic and biological features distinct from other regions within the community; sometimes referred to as a subcommunity .
Population
a collection of organisms of the same species; collection of individuals, all of the same species.
Species
a distinct kind of organism. When populations of two kinds occur together without interbreeding, they are considered different species. When the populations do not occur together, the judgment of whether they belong to different species or are just geographic varieties of the same species can be arbitrary.
Individual
biologically, either 1) an independently living single cell or 2) a group of cells physically attached to one another that have descended from a single cell. Ecologically:
1. Ramet - an ecological unit; the entity that is noticed in the field as an individual, such as a shoot from an underground stem (rhizome), as in beach brass (Amophila breviligulata; vegetative sprouts of a plant from a larger, common portion of a plant (e.g. fiddle heads emerging from the rhizome of a fern, adventitious shoots from a log); or a plant grown from a cutting, as in grape (Vitis spp.). A ramet is ecologically considered an individual unit because it is mostly autonomous with regard to utilization of resources, even though it is physically connected to one or more individuals of the exact same species and identical genetic background; essentially a clone.
2. Genet - a genetically distinct unit; it is all the tissue that grows from a single fertilized egg. A genet may encompass many ramets including ramets that are no longer connected to one another. Sometimes and entire stand of trees, shrubs, etc. may be a single genet if all of the individualls were originally derived vegetatively from a single, parent plant.
Living vs. non-living components of the environment
- Biotic components
  - Definition of life (traditional vs. modern)
  - Kingdoms of life (traditional vs. modern)
- Abiotic components
- Interactions between Biotic and Abiotic components
  Exchange of energy and matter:
  1. Plants tend to be considered decentralized energy receivers and regulators of coupled flows of gasses, water, and other organic and inorganic nutrients.
  2. Animals tend to be considered centralized energy seekers and physically search for food, water, and other nutrients; also regulate flows of gasses, water and nutrients; also tend to regulate their temperature to maintain mobility.
  Specific examples, and additional terms and definitions:
  Abiotic example
  physical characteristic of a habitat such as temperature of the air or water.
  Biotic example
  biological component of a habitat such as a predator, competitor, or mate with which an individual may interact.
  Resource
  an object or an area in the environment that is consumed or used up by an organism and for which competition occurs (e.g. food, space, sunlight).
  
  Renewable - resource that is replenished.
  Non-renewable - resource that is depleted over a period of time.
  
  Habitat
  Microhabitat
  the specific kind of spot where an organism is usually found within its habitat (e.g. milkweed is the microhabitat of the caterpillar stage of monarch butterflies.
  Niche
  the way in which an organism obtains resources; its occupation as opposed to its address (how vs. where); e.g. the caterpillars of monarch butterflies obtain most of their resources by eating, specifically, the leaves of only one species of milkweed and totally relies on that plant for a specific stage of the life cycle.
  Other, more general ways in which organisms obtain resources, specifically energy:
  
  Autotrophically - derivation of energy directly from the physical environment, such as from sunlight or inorganic chemicals.
  
  Phototrophs
  obtain energy from the sun (e.g. plants, algae, cyanobacteria, photosynthetic microorganisms).
  Lithotrophs
  obtain enrgy from the oxidation of reduced inorganic compounds such as NH4 and H2S (e.g. some bacteria).
  
  Heterotrophically - derivation of energy from the oxidation of reduced organic compounds such as glucose, which is produced by photosynthetic organisms (e.g. fungi, many bacteria, and all animals).
Survival: Plants vs. Animals
1. Have to derive energy and food
  - Plant (photoautotrophs; autotrophs) obtain energy from the sun and make food by photosynthesis (primary production).
  - Animals (chemoorganotrophs; heterotrophs) obtain energy and food from other organisms (ultimately from the sun).
2. Have to reproduce
  - Plants reproduce both sexually and asexually.
  - Animals reproduce mostly sexually; some asexually.
Chapter 2, How a plant works: Water, carbondioxide, light, and nutrients.
- Overall plant structure:
  1. Root
  2. Shoot
  3. Canopy
- Water - carbondioxide connection:
  1. CO2 is exchanged through stomatata (hole in plant leaves).
  2. CO2 is mostly taken up by plants and used for glucose synthesis during photosynthesis.
  3. Some CO2 is given off by photorespiration (wasteful oxidation of glucose without production of useful energy in the form ATP)
  4. Ideally, more net CO2 should go into the plant than come out (dependent upon the amount and intensity of light).
  5. Water is usually given off from leaves through the stomata by transpiration.
  6. Water is taken up by the roots and translocated through the root and shoot system by the vascular tissues (specifically the xylem).
  Light is most abundant during the hottest part of the day, therefore, two potential problems exists: excesive water loss occurs if CO2 is taken up exclusively during the day, and photorespiration can occur as well.
  Solutions: some plants suited to hot, dry climates have special anatomical and metabolical adaptations to get around this the water loss / CO2 uptake problem.
  - The C4 pathway solution to the problem of photorespiration:
    In some plants (C4 plants such as corn and sugar cane), the first intermediate of carbon fixation is oxalacetate (OAA; a four-carbon organic acid). OAA is produced in non-photosynthetic cells which lack chloroplasts. The OAA is transported to photosynthetically acitve cells where the OAA is broken down into CO2 and a three carbon compound. The CO2 concentration, therefore increases in the photosynthetically active cells and carbon fixation occurs effeciently without wasteful photorespiration. Under high light, high temperature, and high O2 conditions, photorespiration occurs, and energy and fixed carbon are wasted. But if the CO2 is concentrated in cells deep within the leaves where the O2 concentration is low, photorespiration is less likely to occur.
  - The CAM (crassulacean acid metabolism) plant solution to water loss problem:
    Succulent plants (high water content in fleshy parts of the plant; e.g. cactus) of the family Crassulaceae use the C4 pathway to store up CO2 in the form of OAA during the night while it is cool and then breakdown the OAA to increase the CO2 concentration in leaves during the day. The stomata open at night, allowing CO2 to be taken up and reduce the amount of water lost. The stomata close during the day, but the presence of light and high internal concentration of CO2 allow photosynthesis to occur without loss of water.