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[h] IB DP Biology HL C4.1 Populations and communities Flashcards
[q] C4.1.1—Populations as interacting groups of organisms of the same species living in an area
[a] Students should understand that members of a population normally breed and that reproductive isolation is used to distinguish one population of a species from another.
[q] C4.1.2—Estimation of population size by random sampling
[a] Students should understand reasons for estimating population size, rather than counting every individual, and the need for randomness in sampling procedures.
NOS: Students should be aware that random sampling, instead of measuring an entire population, inevitably results in sampling error.
In this case the difference between the estimate of population size and the true size of the whole population is the sampling error.
[q] C4.1.3—Random quadrat sampling to estimate population size for sessile organisms
[a] Both sessile animals and plants, where the numbers of individuals can be counted, are suitable.
Application of skills: Students should understand what is indicated by the standard deviation of a mean.
Students do not need to memorize the formula used to calculate this.
In this example, the standard deviation of the mean number of individuals per quadrat could be determined using a calculator to give a measure of the variation and how evenly the population is spread.
[q] C4.1.4—Capture-mark-release-recapture and the Lincoln index to estimate population size for motile organisms
[a] Application of skills: Students should use the Lincoln index to estimate population size.
Population size estimate = M × N R , where M is the number of individuals caught and marked initially, N is the total number of individuals recaptured and R is the number of marked individuals recaptured.
Students should understand the assumptions made when using this method.
[q] C4.1.5—Carrying capacity and competition for limited resources
[a] A simple definition of carrying capacity is sufficient, with some examples of resources that may limit carrying capacity.
[q] C4.1.6—Negative feedback control of population size by density-dependent factors
[a] Numbers of individuals in a population may fluctuate due to density-independent factors, but densitydependent factors tend to push the population back towards the carrying capacity.
In addition to competition for limited resources, include the increased risk of predation and the transfer of pathogens or pests in dense populations
[q] C4.1.7—Population growth curves
[a] Students should study at least one case study in an ecosystem.
Students should understand reasons for exponential growth in the initial phases.
A lag phase is not expected as a part of sigmoid population growth.
NOS: The curve represents an idealized graphical model.
Students should recognize that models are often simplifications of complex systems.
Application of skills: Students should test the growth of a population against the model of exponential growth using a graph with a logarithmic scale for size of population on the vertical axis and a nonlogarithmic scale for time on the horizontal axis.
[q] C4.1.8—Modelling of the sigmoid population growth curve
[a] Application of skills: Students should collect data regarding population growth.
Yeast and duckweed are recommended but other organisms that proliferate under experimental conditions could be used.
[q] C4.1.9—Competition versus cooperation in intraspecific relationships
[a] Include reasons for intraspecific competition within a population.
Also include a range of real examples of competition and cooperation.
[q] C4.1.10—A Community as all of the interacting organisms in an ecosystem
[a] Communities comprise all the populations in an area including plants, animals, fungi and bacteria.
[q] C4.1.11—Herbivory, predation, interspecific competition, mutualism, parasitism and pathogenicity as categories of interspecific relationship within communities
[a] Include each type of ecological interaction using at least one example.
[q] C4.1.12—Mutualism as an interspecific relationship that benefits both species
[a] Include these examples: root nodules in Fabaceae (legume family), mycorrhizae in Orchidaceae (orchid family) and zooxanthellae in hard corals.
In each case include the benefits to both organisms.
Note: When students are referring to organisms in an examination, either the common name or the scientific name is acceptable.
[q] C4.1.13—Resource competition between endemic and invasive species
[a] Choose one local example to illustrate competitive advantage over endemic species in resource acquisition as the basis for an introduced species becoming invasive.
[q] C4.1.14—Tests for interspecific competition
[a] Interspecific competition is indicated but not proven if one species is more successful in the absence of another.
Students should appreciate the range of possible approaches to research: laboratory experiments, field observations by random sampling and field manipulation by removal of one species.
NOS: Students should recognize that hypotheses can be tested by both experiments and observations and should understand the difference between them.
[q] C4.1.15—Use of the chi-squared test for association between two species
[a] Application of skills: Students should be able to apply chi-squared tests on the presence/absence of two species in several sampling sites, exploring the differences or similarities in distribution.
This may provide evidence for interspecific competition.
[q] C4.1.16—Predator-prey relationships as an example of density-dependent control of animal populations
[a] Include a real case study.
[q] C4.1.17—Top-down and bottom-up control of populations in communities
[a] Students should understand that both of these types of control are possible, but one or the other is likely to be dominant in a community.
[q] C4.1.18—Allelopathy and secretion of antibiotics
[a] These two processes are similar in that a chemical substance is released into the environment to deter potential competitors.
Include one specific example of each—where possible, choose a local example.
[q] Ecosystems
[a] organisms and their environment (abiotic and biotic)
[q] Community
[a] all organisms living in an area
[q] Population
[a] Same Species, Area, Time
[q] Carrying capacity
[a] Limited resources cause there to be a maximum capacity of animals that an ecosystem can support
[q] Negative feedback
[a] one variable causes a decrease in another variable
[q] Positive feedback
[a] one variable causes an increase in another variable
[q] Density dependent factors
[a] depends on density of population size (will bring it towards the carrying capacity)
Ex. disease, predators, food
[q] Density independent factors
[a] does not depend on population size (causes pop. to fluctuate)
Ex. weather, natural disasters
[q] List all interspecies interactions
[a] Herbivory
Predation
Interspecific competition
mutualism
parasitism
Pathogenicity
[q] Herbivory
[a] Animal eats plant
Ex. Deer
[q] Predation
[a] Animal eats another animal
Ex. Coyotes eat rabbits
[q] Interspecific competition
[a] Two species compete for same resources
Ex. Coyotes and wolves
[q] Mutualism
[a] Two animals increase each others survival
Ex. California oak and fungi
[q] Parasitism
[a] One animal lives on or in another organism and takes its nutrients
Ex. Rockfish and protozoa
[q] Pathogenicity
[a] Spreading disease to another organism
Ex. Avian flu
[q] List 3 IB examples of mutualism
[a] Root nodules in Fabaceae (Bacteria get carbon and legumes get nitrogen)
Mycorrhizae in Orchidaceae (Mycorrhizae Fungi get carbon and orchids get nitrogen)
Zooxanthellae in hard corals (Zooxanthellae get protection and coral gets nutrients like glucose)
[q] Predator-prey relationship
[a] example of density-dependent control of animal populations
As one goes up the other goes down
Form of negative population control
Most common example is the lynx and the hare
Time lag – gap between changes
[q] Intraspecific competition
[a] Competition among members of the same species
Ex. male zebras, tigers, bears, male antelopes, eagles, hawks.
[q] Cooperation
[a] individuals of a species work together to increase survival
Ex. wolves, humans, ants, bees
[q] Top down control
[a] predators limit population size
[q] Bottom up control
[a] nutrients in ecosystem limit population sizes
Ex. Phytoplankton
[q] Allelopathy
[a] Plants produce toxic compounds that affect the growth of other plants
Can be transferred by: rain, release as a gas, dead leaves
Ex. Black walnut, mustard
[q] What do some plants secrete?
[a] Antibiotic compounds
Ex. California bay and coffeeberry
[q] List 2 population growth curves
[a] Exponential: Most populations start exponential because there is an abundance of resources
logistic/sigmoid growth: Starts to flatten as resources become limited
[q] How do you estimate a population size?
[a] random sampling
[q] How do you estimate population size for sessile organisms?
[a] Sessile – not moving
Random quadrat sampling
Make a grid and then sample random squares to estimate the total population
Count how many are in the squares and then multiply by
Total squares divided by squares sampled to get estimate
[q] Chi Square test – You find they are present together twice, pine tree is found alone 45 times, maple is found alone 33 times and they are both absent a total of 10 times.
Is there an association between maple and pine?
[a]
[q] Capture-mark-release-recapture and the Lincoln Index
[a] First you capture animals, mark them, release them and then wait and recapture them and count how many you captured and specifically how many were marked.
Then you use the lincoln index to estimate population size!
[q] Name types of tests for interspecific competition
[a] Lab experiments – trying growing them together and see what happens
Field experiments observation – use random sampling and chi squared
Field experiments manipulation – remove species and see what happens
Null hypothesis – no correlation between species
Alternative hypothesis – there is a correlation (most likely negative)
[q] Name an example of resource competition between endemic and invasive species
[a] If an invasive species can outcompete native species then it leads to the native species to become threatened
e.g. Red eared slider and Western Pond Turtle
[q] Limiting Factor
[a] -a component of an ecosystem which limits the distribution or numbers of a population
-defines optimal survival conditions according to its effect on a species when in deficiency or excess
-either biotic or abiotic
[q] Examples of Biotic factors
[a] -interactions between organisms – either intraspecific (within species) or interspecific (between species)
[q] Examples of abiotic factors
[a] environmental conditions – such as light, temperature, salinity, rainfall, wind velocity, soil pH, etc.
[q] Law of Tolerance
[a] -proposed by Victor Ernest Shelford
-According to the law of tolerance, populations have optimal survival conditions within critical minimal and maximal thresholds
-As a population is exposed to the extremes of a particular limiting factor, the rates of survival begin to drop
-Distribution of a species in response to a limiting factor = bell curve w/ 3 distinct regions:
[q] Optimal zone
[a] Central portion of curve which has conditions that favor maximal reproductive success and survivability
[q] Zones of stress
[a] Regions flanking the optimal zone, where organisms can survive but with reduced reproductive success
[q] Zones of intolerance
[a] Outermost regions in which organisms cannot survive (represents extremes of the limiting factor)
[q] Plant example:
[a] -plant growth varies greatly in response to salt concentrations in soil
-glycophytes = Plant species that are not particularly salt tolerant
-halophytes = Plant species that are salt tolerant (but stressed in fresh
-most plants are considered glycophytes
-Cultivation of land concentrates salt at roots
-This makes it harder for glycophytes to get water from the soil
[q] Animal Example:
[a] -coral species are greatly impacted by oceanic temp.
-increased temp. can lead to coral bleaching
-Reef-building coral species therefore have a typical optimal growth range in temperate waters between 20 – 30ºC
-tropical and subtropical regions of the world
[q] What measures the distribution of a plant or animal species in response to an incremental abiotic factor?
[a] -Quadrats and transects
-Quadrats: rectangular frames of known dimensions that can be used to establish population densities
-Transects: a straight line along an abiotic gradient from which population data can be recorded to determine a pattern
-Quadrats can be placed at regular intervals along the transect line in order to generate population data
-quadrats will show the changing distribution pattern of a species in response to a change in an abiotic variable
-data can be used to identify optimal conditions as well as zones of stress and zones of intolerance
[q] Transect Data
[a] -transects used to assess species distribution in correlation with any abiotic factor that varies across a measurable distance (factors could include: elevation, elemental exposure, temperature, light levels, pH, humidity and more)
[q] A kite graph
[a] -used to represent changes in species distribution in a clear and effective fashion
-relative width of each ‘kite’ represents the abundance of an organism at a particular point along a transect
[q] ecological niche
[a] -describes the functional position and role of an organism within its environment
-consists of all physical and biological conditions which determine the organism’s survival and reproductive prospects
[q] elements of an ecological niche
[a] -The habitat in which an organism lives
-The activity patterns of the organism
-The resources it obtains from the environment
-The interactions that occur with other species in the community
[q] What happens if two distinct species share an identical niche?
[a] -there will be interspecific competition for available space and resources
-competition between the two species will result in the fitness of one being lowered by the presence of the other
-the less well-adapted species will struggle to survive and reproduce
[q] Interspecific competition within a shared niche usually causes:
[a] -Competitive exclusion
-Resource partitioning
[q] fundamental niche
[a] -the entire set of conditions under which an organism can survive and reproduce (where it could live)
-the theoretical niche
-may not be fully occupied due to the presence of competing species
[q] Realized Niche
[a] -the set of conditions used by an organism after including interactions with other species (where it does live)
-the actual habitat that is completely occupied by an organism in the presence of competing species
[q] Herbivory
[a] -the act of eating only plant matter (ex. primary consumers)
-can be either harmful or beneficial to the plant species as a whole:
-ex. beetles causing crop failure
-ex. fruit-eating animals spreading seeds
[q] Predation
[a] -a biological interaction whereby one organism (predator) hunts and feeds on another organism (prey)
-predator relies on the prey as a food source
-population levels are inextricably intertwined
[q] Symbiosis
[a] -the close and persistent interaction between two species
-Symbiotic relationships can be obligate (required for survival) or facultative (advantageous without being strictly necessary)
-can be beneficial to either one or both organisms in the partnership
[q] Mutualism
[a] Both species benefit from the interaction
e.g. anemone protects clownfish, clownfish provides fecal matter for food
[q] Commensalism
[a] One species benefits, the other is unaffected
e.g. barnacles transported to plankton-rich waters by whales
[q] Parasitism
[a] One species benefits to the detriment of the other species
e.g. ticks or fleas feed on the blood of their canine host
[q] Relationship Between Zooxanthellae and Reef-Building Coral Reef Species
[a] -Reef-building coral will form a symbiotic relationship algae Zooxanthellae
-The algae lives within the cells of the coral’s endodermis
-The coral provides the algae with a protective environment and source of inorganic compounds
-The zooxanthellae provides the coral polyps with a necessary source of nutrition (oxygen, glucose and other organic molecules)
[q] Coral Bleaching
[a] -zooxanthellae gives the coral its vibrant pigmentation
-large scale loss of zooxanthellae causes bleaching
-When bleaching occurs, coral begins to starve and will die unless the zooxanthellae are restored