Topic 4 - Ecology Flashcards
Species
Proposed by Ernst Mayr, the biological species concept defines a species as organisms that can (actually or potentially) interbreed with each other to produce fertile offspring and cannot breed with others. In other words, the organisms of the species are reproductively isolated.
Describe limitations of the biological species concept.
- Cannot test the reproductive isolation of fossils which must be classified into species based on morphology.
- Even for living species, it is hard to determine if populations are reproductively isolated especially if they are geographically isolated.
- Many species, especially prokaryotes, reproduce asexually and must be classified based on morphology and/or biochemical characteristics.
Define “reproductive isolation.”
Reproductive isolation is the inability of a species to interbreed successfully with other species due to geographical, behavioral, physiological, or genetic barriers.
Define “population.”
A population is organisms of the same species that live in a particular geographic area at the same time.
Define “speciation.”
Speciation is the process by which populations evolve to become distinct species no longer capable of interbreeding with each other to produce fertile offspring.
Outline how reproductive isolation can lead to speciation.
- Geography, changes in behavior or polyploidy can cause reproductive isolation between populations, isolating the gene pools
- Natural selection acts on the isolated populations independently
- The populations diverge to the point of no longer being able to interbreed with each other to produce fertile offspring, forming two species
Define “autotroph.”
An autotroph is an organism capable of making energy-containing organic molecules from inorganic sources via photosynthesis (involving light energy) or chemosynthesis (involving chemical energy). Autotrophs are the producers in a food chain, such as plants or algae.
Define “heterotroph.”
A heterotroph is an organism that is unable to synthesize its own organic compounds from inorganic sources, and as a result must feed on organic matter produced by, or available in, other organisms.
Describe the feeding behaviors of consumers.
Consumers are organisms that need to eat food to obtain their energy. All heterotrophs are consumers.
List three example consumer organisms.
Any organism that is not an autotroph (producer) is a consumer. In this food web, all organisms besides the phytoplankton and seaweed are consumers.
Describe the feeding behaviors of detritivores.
Detritivores are heterotrophs that obtain nutrients by consuming detritus. Detritus is particulate organic material such as the bodies or fragments of dead organisms and/or fecal material.
List two example detritivore organisms.
Some example detritivores include earthworms, millipedes, dung beetles, sea cucumbers and fiddler crabs.
Describe the feeding behaviors of saprotrophs.
Saprotrophs live on dead organic matter and feed by a process in which dead or decaying organic material is extracellularly digested (outside of the cell) by a variety of enzymes that are excreted by the organism. After digestion, the nutrients are then absorbed into the organism.
Explain the role of saprotrophs in an ecosystem.
In the ecosystem, saprotrophs recycle nutrients by breaking down organic material into inorganic material. Saprotrophs improves soil fertility by returning nutrients (such as minerals, nitrates, phosphates) to the environment.
Saprotrophs release heat energy that in turn accelerates decomposition by warming the soil.
List two example saprotroph organisms.
Some example saprotrophs include fungi and soil bacteria.
Define “community.”
A community is all the populations of various species living and interacting in a common location.
Give an example of a community of organisms.
A tropical forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi, constitutes a biological community.
Define “abiotic.”
Abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors such as climate and geology can determine which species of organisms will survive in a given environment.
Define “ecosystem.”
An ecosystem is the interaction of the community of living organisms with the abiotic components of their environment. The biotic and abiotic components are of an ecosystem are linked together through nutrient cycles and energy flows.
Define “nutrient.”
Nutrients are molecules required by an organism for growth, repair, and normal metabolism.
List the common nutrients needed by organisms.
Macronutrients (carbohydrates, fats, proteins and water) are needed in large amounts and are used primarily to generate energy or to incorporate into tissues for growth and repair.
Micronutrients (minerals and vitamins) are needed in smaller amounts and often have subtle biochemical and physiological roles in cellular processes.
Outline how nutrients enter living systems.
Through a nutrient cycle a nutrient is able to move from inorganic matter back into a living system. In this example, the process is initiated by an autotroph which synthesizes organic molecules which then move through food web pathways. Eventually the nutrient convert back into inorganic nutrients through metabolism or decomposition.
State that chemical elements can be recycled but energy cannot.
Chemical nutrients and energy tend to flow in the same direction for most of an ecosystem (from autotrophs to heterotrophs). The big difference is that the chemical nutrients can be recycled in the ecosystem while the energy is ultimately lost from the ecosystem to the universe at large.
Outline the generalized flow of nutrients between the abiotic and biotic components of an ecosystem.
Elements such as carbon, nitrogen, oxygen, and hydrogen are moved through biotic components of an ecosystem through food chains and recycled through abiotic environments including the atmosphere, water, and soil.
Define “sustainability.”
Sustainability is the capacity of ecosystems to maintain their essential functions and processes, over time.
Give an example of an unsustainable practice.
Unsustainable practices are not able to be maintained at the current rate or level.
Examples include:
Pollution and contamination of air, land, and water.
Deforestation.
Soil degradation and erosion.
Wasteful consumption of water.
Outline three requirements of a sustainable ecosystem.
Sustainable ecosystems require nutrient availability , an ability to detoxify waste products and a supply of energy.
Use a dichotomous key to identify the mode of nutrition of an organism.
A dichotomous key is a tool that allows the user to determine the identity of an organism by following a series of steps.
Outline why sampling must be random.
In ecology research it is very difficult to count/measure all individuals in a population, community or ecosystem. Random sampling eliminates bias and allows researchers to make generalizations about a larger system, making the assumption that these samples are representative of the ecosystem in general.
Explain methods of random sampling, including the use of a quadrat.
In quadrat sampling, a number of random samples are taken from around the habitat using a standard sampling unit. Quadrats normally consist of a square frame. The frame is placed (on the ground or on whatever is being investigated) and the animals, and/ or plants inside it counted, measured or collected. This is done many times at different points within the habitat to give a large number of different samples.
Use a contingency table to complete a chi-square test of association.
The chi-square test of association is used to determine whether there is a significant association between the two species within a habitat. The data is displayed in a contingency table where each row represents a category for one species and each column represents a category for the other species.
Calculate a chi-square statistic based on observed and expected values.
- Calculate the expected values for the two species, assuming the species are randomly distributed with respect to each other. Expected frequencies = (row total X column total) / grand total
- Apply the formula to calculate the value of the Chi-Square test of Independence
- The calculated X2 value is than compared to the “critical value X2” found in an X2 distribution table. The X2 distribution table represents a theoretical curve of expected results. The expected results are based on DEGREES OF FREEDOM. DF = (rows-1)(columns-1)
State the null and alternative hypothesis of statistical tests.
Null hypothesis: Assumes that there is no association between the two variables.
Alternative hypothesis: Assumes that there is an association between the two variables.
Determine if the null hypothesis is supported or rejected given a critical value and a calculated statistic.
If the calculated value is lower than the critical value at the 0.05 level of significance, accept the null hypothesis and conclude that there is NO significant association between the variables.
If the calculated value is higher than the critical value at the 0.05 level of significance, reject the null hypothesis and conclude that there IS a significant association between the variables.
State the minimum acceptable significance level (p value) in published research.
In the majority of analyses, a p value of 0.05 is used as the cutoff for significance. If the p-value is less than 0.05, we reject the null hypothesis that there’s no difference between the means and conclude that a significant difference does exist.
Define “p-value” in relation to tests of statistical significance.
The significance level, p, is the probability of obtaining a result at least as extreme, given that the null hypothesis were true.
A significance level of 0.05 indicates a 5% risk of concluding that a significant result exists when there actually isn’t one..
Explain the meaning of a “statistically significant” result.
A “statistically significant” result is one in which there is a very low probability (usually less than 5%) that the observed effect would have occurred due to sampling error alone.
Define “mesocosm.”
A mesocosm is an experimental model ecosystem used to investigate ecosystems under controlled conditions.
List three example mesocosms.
Mesocosms can take many shapes and forms, such as:
- small sealed containers with organisms inside it
- fenced enclosures in fields or aquatic areas
- large tanks with inputs and outputs that mimic environmental conditions.
State the trend found in the nutritional patterns of plants and algae.
The majority of plants and algae are autotrophs capable of making their own carbon compounds by photosynthesis.
Describe the discrepancy in the nutritional pattern of parasitic plants and algae.
There are a few types of plants and algae that do not perform photosynthesis and instead are parasitic on other plants, obtaining their nutritional requirement from another living plant.
Parasitic plants have modified roots which penetrates the host plants, providing them with the ability to extract water and nutrients from the host.
State how energy in carbon compounds enters most biological communities.
In most ecosystems, chemical potential energy stored in carbon compounds enters biological communities through photosynthesis in producers.
List three groups of autotrophs.
Autotrophs are organisms that produces complex organic compounds from inorganic substances, generally using energy from light or inorganic chemical reactions.
Common autotrophs are:
-plants
-algae
-cyanobacteria
Outline how light energy is converted to chemical energy.
Light energy is converted to chemical energy through photosynthesis. Producers absorb wavelengths of light using photosynthetic pigments and convert this light energy into chemical energy.
Define “food chain.”
A food chain is a sequence of organisms through which nutrients and energy pass as one organism eats another. Food chains show which organisms eats which organism. Food chains always begin with a producer and follow the flow of energy through trophic levels.
Define “food web.”
A food web represents the interconnected feeding relationships within an ecological community.
State the meaning of the arrow in a food web or chain.
Arrows in food chains and webs represent the flow of energy and nutrients through the trophic levels.
Outline the flow of energy through a food chain.
- Light energy is converted by an autotrophs to chemical energy stored in carbon compounds (such as glucose) through photosynthesis.
- Energy is transferred to other organisms through feeding; producers are eaten by primary consumers, these by secondary consumers, these by tertiary consumers…
- Cellular respiration releases energy from the carbon compounds to produce ATP for use by organisms for metabolism, growth, repair, and/or movement
- Approximately 90% of the energy at each trophic level is lost as heat, biomass not consumed (i.e. bones/hair) or biomass lost as waste (i.e. in feces/urine)
Energy is NOT recycled!
Draw a food chain, labeling the producer, primary consumer, secondary consumer and tertiary consumer.
When drawing a food chain, begin with a producer. Draw an arrow to the organism(s) that eats the producer, called the primary consumer. Draw additional organisms and arrows to represent the chain of feeding, from the primary consumer to the secondary consumer and from secondary consumer to the tertiary consumer.
List three reasons why living organisms need energy for cell activities.
Maintaining a living system requires an input of energy for cell activities such as synthesizing large molecules (such as DNA and proteins), active transport of molecules and ions across the cell membrane, movement of structures within the cell (such as vesicles and chromosomes) and contraction of proteins (such as during cytokinesis).
