Populations and Communities Unit Final Flashcards
What are alleles?
Alternate forms of the same gene
Alleles can influence traits in different ways depending on their dominance or recessiveness.
Define homozygous.
When the 2 alleles at a locus are identical
Homozygous individuals can be either dominant or recessive.
What is Population Crash?
When a population decreases very rapidly
Define microevolution.
The gradual change in allele frequencies in a population
None
Define parasites.
Organisms that live on or in a host organism at the expense of the host
What processes cause changes in gene pools? (5)
- Genetic mutations
- Gene flow
- Non-random mating
- Genetic drift
- Natural selection
What is phenotype?
The physical and physiological traits of an organism
Phenotype is influenced by both environment and heredity.
whatās a trophic cascade?
an ecological phenomenon where the addition or removal of a top predator causes a ripple effect throughout an ecosystem, impacting populations at multiple trophic levels
How many sets of chromosomes do individuals generally have?
2 sets of chromosomes
One set from the male parent and one from the female parent.
What does the Theory of Evolution by Natural Selection state?
New variants of species arise continually in populations
Some variants thrive while others die off based on their ability to adapt to the environment.
Define allele frequency.
The rate of occurrence of a particular allele in a population with respect to a particular gene
None
What are mutations?
Permanent changes in the genetic material of an organism
Mutations can lead to new traits or variations in a population.
Why is the Hardy-Weinberg principle valuable?
It can be used to measure the amount of change in the allele frequencies of a population over time.
What is a species?
Structurally similar organisms that can mate and produce fertile offspring in nature.
What is secondary succession?
The recolonization of an area after an ecological disturbance, where soil is not usually destroyed
What effect does gene flow have on genetic diversity?
Increases genetic diversity in one population but reduces genetic differences among populations.
What is genetic variation?
Substantial genetic variation within populations
Genetic variation is essential for evolution and is caused by random genetic mutation and natural selection.
What are genes?
Carried on chromosomes and control the inheritance of traits
None
What are the three forms of symbiosis?
- Mutualism
- Commensalism
- Parasitism
In the Hardy-Weinberg equation, what does āqā represent?
Recessive alleles
None
Characteristics of r-Selected Strategies? (3)
- Short life span
- Early reproductive age
- Large broods of offspring with little parental care
What is Immigration?
The movement of individuals into a population
What is random mating?
When there is no way to predict which males will mate with which females.
What is a climax community?
The last or final stage of succession in an area, remaining stable unless disturbed
What does the Hardy-Weinberg principle provide?
A basis for studying allele frequencies and genotype frequencies in a gene pool
None
What is the bottleneck effect?
Gene pool change that results from a rapid decrease in population size.
What is intraspecific competition?
Competition for limited resources among members of the same species
What is phenotype frequency?
The proportion of a population with a particular phenotype.
What are the representations of genotypes in the gene pool? (3)
- p2 = frequency of homozygous dominant genotype
- 2pq = frequency of heterozygous genotype
- q2 = frequency of homozygous recessive genotype
None
What is Carrying Capacity?
The theoretical maximum population size that the environment can sustain
what does the negative symbol on a trophic cascade diagram mean
it shows that the effect is negative
How can populations be described in terms of life strategies?
Most populations have a combination of r and k selected strategies
What is a recessive allele?
The allele that has no noticeable effect on the organismās appearance when 2 different alleles are inherited
Recessive alleles can only manifest in the phenotype if an individual is homozygous for that allele.
How does variety in the gene pool affect population survival?
The more variety in the gene pool of a population, the better chance the population can survive in a changing environment
None
List the five conditions for the Hardy-Weinberg Principle.
- Population is large enough that chance events will not alter allele frequencies
- Mates are chosen on a random basis
- There are no net mutations
- There is no migration
- There is no natural selection against any of the phenotypes
None
What is the founders effect?
The gene pool change that occurs when a few individuals start a new isolated population.
Define population dynamics.
The changes that occur in populations over time
What is an ecological disturbance?
An event that changes the structure of a community and sometimes destroys all actively growing organisms
What are boom or bust cycles?
Cycles observed in predator-prey populations where increases in prey lead to increases in predators, followed by a decline in prey due to increased predation
What is an ecological community?
Association of interacting populations that inhabit a defined area
What are Abiotic Factors?
Non-living components of an ecosystem
What is genetic diversity?
The degree of variation within a species or population.
Define Ecosystem.
The interaction between living organisms and their environment
What is a dominant allele?
The allele that is expressed in the individualās appearance when 2 different alleles are inherited
Dominant alleles mask the effects of recessive alleles.
What is Lag Phase?
When the growth of a population is slow at the beginning
whats a community
all the interacting populations of different species living in the same area
What is interspecific competition?
Competition between two or more populations for limited resources
How do human activities impact genetic diversity?
Through habitat fragmentation and unregulated hunting.
What is protective coloration?
Body colour as a natural defence mechanism
What is parasitism?
A form of symbiosis where one partner benefits at the expense of its host
What causes microevolution? (5)
- Inheritable mutations
- Gene flow
- Non-random mating
- Genetic drift
- Natural selection
What is primary succession?
The development of a new community in a previously barren area where there is no soil present
Define genotype.
Genetic makeup of an individual that remains constant throughout its life
Genotype determines the potential traits an organism can express.
What are Biotic Factors?
Living things within an ecosystem
What is Biotic Potential?
The highest possible per capita growth rate for a population
What is Per Capita Growth?
Change in population size per individual over a given time frame
What does a gene pool contain?
All the alleles for all the genes in a population that can be passed on to the next generation
None
What role does intraspecific competition play in ecology?
It is a density-dependent factor that limits the growth of a population and plays an important role in natural selection
What is Emigration?
The movement of individuals out of a population
How can you calculate the number of individuals with a particular genotype?
Using: p2(N) + 2pq(N) + q2(N) = N
None
Define Growth Rate.
The change in the number of individuals in a population over a specific time frame
What is Population Density?
The number of individual organisms in a given area or volume
Why can no two species share the exact same ecological niche?
Due to interspecific competition
What are the two extreme causes of genetic drift?
- Founder effect
- Bottleneck effect
What is a Density-Independent Factor?
Abiotic factor that limits a habitatās carrying capacity, not affected by population density
Characteristics of Clumped Distribution?
Members of a population are found in close proximity in groups within their habitat
What happens to producer populations when there is a dense population of consumers?
The consumer population may control the growth of producer populations
What does genotype frequency refer to?
Proportion of a population with a particular genotype
None
What are age pyramids?
Tools that demographers use to help them assess a populationās potential for growth
Age pyramids display the distribution of males and females across different age categories.
What is a mutation?
A change that occurs in the DNA of an individual.
What does an upright triangle-shaped age pyramid indicate?
There are more births than deaths in the population and therefore the population is growing rapidly
This shape suggests a young population with high fertility rates.
what does a dashed arrow mean on a trophic cascade diagram
the species disappearance had an indirect effect on another species
Characteristics of K-Selected Strategies?
- Few offspring per reproductive cycle
- Parental care for young
- Long maturation time
- Long lifespan
What do the frequencies of dominant and recessive alleles represent?
p2 + 2pq + q2 = 1.00
None
What does an inverted triangle-shaped pyramid indicate?
The population is declining
This shape suggests lower birth rates and an aging population.
What is genetic equilibrium?
When there is no change in allele frequencies over time so the population is not changing or evolving
None
What can inbreeding result in?
A severe limitation of genetic diversity in gene pools.
Define secondary consumer.
Organism that eats primary consumers
what does a positive symbol on a trophic cascade idagrma mean
changes in the population of the first species is mirrored by the population changes of the second species
What are the three types of biodiversity?
- Species diversity
- Genetic diversity
- Habitat diversity
What is the Hardy-Weinberg Principle?
A principle that shows that allele frequencies in a population will remain the same from one generation to the next as long as 5 conditions are met
None
What is a Density-Dependent Factor?
Biotic factor that limits a habitatās carrying capacity and increases with population density
What factors influence distribution patterns of populations?
The distribution of resources in a habitat and the interactions among community members
whatās a keystone species?
a species on which other species in an ecosystem largely depend, such that if it were removed the ecosystem would change drastically
How do you calculate the total number of alleles in a population?
The total number of alleles in a population is twice the number of individuals
None
What is Random Distribution?
Occurs when resources are very abundant and population members do not have to compete with one another
What does evolution refer to in biology?
Change in allele frequencies in a gene pool over time.
what is population characterized by?
- the tendency to remain stable and not evolve
- the tendency toward variability and to evolve
What is a back mutation?
A mutation that reverses the effects of a former mutation.
What is Population Explosion?
When a population grows so rapidly that it spreads before it can be contained
What is the heterozygote advantage?
A survival benefit for individuals who inherit two different alleles for the same trait.
Factors determining Biotic Potential?
- Number of offspring per reproductive cycle
- Number of offspring that survive long enough to reproduce
- Age of reproductive maturity
- Number of times an individual can reproduce in a lifespan
- Life span of the individual
What drives population dynamics?
Interactions among individuals within the same population or from different populations
True or False: Random mating is common in natural populations.
False.
What is the effect of inbreeding on homozygous genotypes?
Increases the frequency of homozygous genotypes.
What is an ecological niche?
All the biotic and abiotic factors required for the organism to survive and its interactions with other species
What is commensalism?
A symbiotic relationship where one partner benefits and the other is neither helped nor harmed
What characterizes Logistic Growth Pattern?
Growth is slow at first, steepens in an exponential pattern, then levels off
Causes of Environmental Resistance?
- Decreasing oxygen supply
- Low food supply
- Disease
- Predators
- Limited space
What does a rectangle-shaped pyramid represent?
A stable population
This indicates a balance between births and deaths.
What is adaptation in biology?
The act of changing something or changing behaviour to adjust to new environments or changes in a current environment.
What is a gene pool?
Sum of all the alleles for all the genes in a population
None
What is Exponential Growth Pattern?
Pattern exhibited by a population which is increasing exponentially, resulting in a J-shaped curve
What information do age pyramids provide?
They show the percent of males and the percent of females in different age categories
This helps in understanding the demographic structure of a population.
What occurs during the Exponential Growth Phase?
Birth rate is much higher than death rate, causing rapid growth
What is sustainability?
The concept of living in a way that meets our needs without compromising the health of future generations or the health of the planet
Sustainability focuses on balancing current resource use with future needs.
What is natural selection?
Process where characteristics of a population change over time due to individuals with advantageous traits surviving and reproducing.
What does locus refer to in genetics?
Location of a gene on a chromosome
Each gene has a specific position on a chromosome known as its locus.
Define heterozygous.
When there are 2 different alleles at a locus
Heterozygous individuals express the dominant allele in their phenotype.
Processes that change population size?
- Births
- Immigration
- Deaths
- Emigration
Define primary consumer.
Organism that obtains energy by eating plants, also known as an herbivore
What are predators?
Organisms that kill and consume other organisms
Define biodiversity.
The variety of all living things and their interactions.
Define allele.
The different forms of a gene
None
What is gene flow?
The net movement of alleles from one population to another due to the migration of individuals.
What is a pioneer community?
The first species to colonize a barren or disturbed habitat and initiate primary succession
What is Environmental Resistance?
The combined effects of various limiting factors on population growth
how is the structure of an ecosystem represented
by a pyramid made up of trophic levels such that producers on the bottom, followed by primary consumers, secondary consumers and so on
Define Stationary Phase.
When the birth and death rates are equivalent
whatās a trophic level?
each of several hierarchical levels in an ecosystem, comprising organisms that share the same function in the food chain and the same nutritional relationship to the primary sources of energy
What is mutualism?
A symbiotic relationship where both partners benefit
What happens to variants that thrive in a population?
They produce more offspring which slowly changes the population
This process can lead to the emergence of a new species over time.
What does the total of the allele frequencies for one gene locus always equal?
1.00 or 100 percent of the alleles
None
What is non-random mating?
Mating based on mate selection due to phenotype selection or because of inbreeding.
What provides the population with variation?
Random genetic mutation
These mutations introduce new alleles into a population, contributing to genetic diversity.
What is Uniform Distribution?
When individuals in a population are evenly distributed over a defined area
What is required for a population to be at genetic equilibrium according to the Hardy-Weinberg principle?
The population must be large enough, there must be random mating, no net mutations, no migration, and no natural selection
None
What is a population?
A group of organisms of the same species that live together in a defined area and time
None
Define habitat.
The natural home or environment of an animal, plant, or other organism.
What is genetic drift?
A change in allele frequencies due to chance events in a small breeding population.
What is an inheritable mutation?
A mutation that has the potential to affect an entire gene pool.
What are the three stages of human development according to age pyramids?
- Pre-reproductive stage (0-14 years)
- Reproductive stage (14-44 years)
- Post-reproductive stage (45 years and older)
These stages represent different population dynamics.
What is a host?
An organism that harbours another organism, providing it with nourishment and shelter
What is succession in ecology?
The sequence of invasion and replacement of species in an ecosystem over time
Describe producer-consumer interactions.
Primary producers have a direct relationship with primary consumers who eat them, and primary consumers have a direct relationship with their predators
What is ecology?
The study of relationships between living organisms and their environment.
What does the Hardy-Weinberg principle represent?
An ideal situation that rarely occurs in natural populations.
In the Hardy-Weinberg equation, what does āpā represent?
Dominant alleles
None
What is inbreeding?
Occurs when closely related individuals breed together.
What does natural selection interact with?
Other microevolutionary processes to lead to the evolution of adaptations.
What are prey?
Organisms that are killed and consumed by other organisms
How do you calculate the frequency of each allele?
Divide the incidence of the allele by the total number of alleles in the sample
None
What does variation refer to in biology?
The difference between individuals of the same species.
What is population genetics?
The study of genetic diversity in populations.
What does phenotype frequency measure?
Proportion of a population with a particular phenotype
None
what does a solid arrow mean on a trophic cascade diagram?
the species disappearance had a direct affect on another species
