Population Dynamics And Hardy Weinberg Flashcards
Population
Refers to all members of a particular species living in the same area
Population Ecology
Refers to the study of factors affecting the size and distribution of individuals within a population
Population Density
Is a measure of the number of individuals living in a given area or volume
Density Equation
D=N/A where
D= density
N=the population
A= the area or volume measured
Low density
Individuals are well spaced apart, highly territorial, solitary mammal species
High density
Individuals are crowded together, there are many individuals close together, there is a division of labour and they depend on one another (ant colony)
Measuring density
Estimates are made, quadrants are set up in the larger area. The number of individuals in each quadrant are counted and the results are extrapolated to the larger area
Population Dispersion
Dispersion refers to the patterns of spacing between individuals in a species
Uniform Dispersion
Distribution may result from competition for resources. Individuals are evenly spaced out so that they have control over the resources in their immediate area. Animals are territorial and do not want to share resources, resources are relatively abundant.
Clumped dispersion
Caused by patches of resources in specific areas or by behavioural interactions between memembers of a species. Not territorial, resources are not abundant
Random Distribution
An unpredictable, patternless dispersion. Caused by the lack of a strong attraction or repulsion between members of a species, resources are abundant
Positive population growth
Caused by births and immigration
Negative population growth
Caused by deaths and emigration
Population growth formula
change in N= (#births+#immigrants)-(#deaths+emigrants)
Population Growth Rate
How fast a population is growing, can be positive or negative.
Gr= change in N/ change in t
N: change in population
t: change in time
Per Capita Growth
Cgr: change in N/N
Change in the population/the initial population
This measures the rate of growth in a population in comparison to the size of the population
Density Dependent Factors
These are factors that affect the growth of a population.
Ex: if there is a high density population there will be less food available and greater chance of disease
Tend to be biotic factors (living)
Density independent Factors
Factors affecting a population that are not related to the density of that population.
Ex: bad weather or natural disaster will affect both dense populations and populations that are not dense
Factors tend to be abiotic (not living)
Biotic potential (intrinsic growth)
Rate at which a population will naturally increase under ideal conditions.
Factors affecting biotic potential
Number of offspring per reproductive cycle, number of offspring that live to reproduce, age of sexual maturity, number of times they reproduce in their life, and the Average life span
Carry Capacity (K)
The maximum number of individuals that can be sustained in a particular environment. Reflection of the amount of available food, the existence of predators
Affected by both density dependent and density independent factors
Can change from year to year
Environmental resistance
Environmental factors that resist the growth of a population. Prevents a population from growing at its biotic potential and determines the carrying capacity of the ecosystem.
Consists of predators and disease
Exponential Growth
Exponential growth curve or J curve. G=rN (r=biotic potential) (N=the population)
population increases so does the rate of growth unstable
Population is regulated by density independent (abiotic) factors, involves periods of rapid increase followed by periods of rapid decline
Logistic Growth
More realistic model as a population cannot continue to increase at an exponential rate forever. S shaped curve, controlled by density dependent factors.
size of population increases rate of reproduction decreases
When the population reaches carrying capacity, population growth stops
Overshooting Capacity
Population may temporarily increase above carrying capacity, is usually followed by a crash (dramatic decrease in deaths)
K population Strategy
Selected populations are found where environmental conditions are stable and are characterized by intense intraspecific competition.
(Slow development, few offspring, logistic growth)
R population Strategy
Selected populations undergo many changes and are characterized by high birth rates and a short life span
Ex: insects
(Rapid development, large number of offspring, exponential growth)
Age Pyramid Diagrams
Provides information about a population relating to: male vs females, age group composition of population, growing patterns (increasing, stable, decreasing), natality and mortality
Intraspecific Competition
Competition among individuals of the same species for limited resources
Interspecific Competition
Competition between two different species for the same resource
Gauses principle
No two species can occupy the same ecological niche without one or the other being reduced in numbers or totally eliminated
Competitive Exclusion Principle
Gauses studies indicate that when two species compete for the same resource one will use the resource more efficiently than the other and thus reproduce mode rapidly. This will eventually lead to the elimination of the inferior competitor
Predator Prey Relationship
Tend to mirror each other
When prey population is large, will attract predators and it’s population will increase, prey population will decrease. When the prey population is small, there will be no food for the predator and it’s population will decrease
Symbiosis
a close association between members of 2 different species
Parasitism
One benefits, one is harmed
Tapeworm living in the gut of a mammal
Mutualism
Both organisms benefit
Lichen and fungus and Algae
Commensalism
One benefits, and one is not effected
Bird builds a nest in a tree
Cryptic Coloration
Camouflage
Aposematic Coloration
Conspicuous colours to warn other organisms in the wild that you are dangerous.
Ex: Diamondbacks
Mimicry
Where one species mimics the characteristics of another species that is distasteful or dangerous
Bayesian mimicry
Where a particular species comes to resemble another well protected species (1 dangerous and 1 not)
Mullerian Mimicry
2 dangerous species come to resemble each other, both species benefit because if one of them is attacked a predator will learn to avoid both species because they look the same
Protective Coloration
Colouring to render protection (2 types)
Succession
Sequence of invasion and replacement of species in an ecosystem over time.
as succession progresses, variation in an ecosystem increases
Primary succession
Occurs when there is no soil present, like what is left when a glacier recedes.
Ie: there was nothing living there before
Secondary Succession
Occurs when there was previously life in an area before, but it was wiped out.
Ex: the regrowth of an area after a forest fire, the soil was not killed by the disturbance and still contains nutrients
Pioneer Community
The first species to invade an area and begin succession
Climax Community
The last species to invade an area and complete succession
Gene pool
Refers to the collection of all alleles in the members of the population
Population Genetics
Refers to the study of the genetics of a population and how the alleles vary with time
Hardy Weinberg Principle
States that if 5 conditions are met, the allele frequencies within a population will not change over time (genetic structure of a population will remain the same)
5 ways a populations genetics can change over time
Population is small
Non-random mating
Mutations occurring
Natural or Artificial selection is taking place
Migration (immigration or emigration) of individuals into or away from the population
Small Population
If a population is not sufficiently large, allele frequencies can change due to chance. Referred to as genetic drift, which is much more likely in small populations
Bottleneck effect
Genetic drift resulting from the reduction of a population, typically by a natural disaster. Can result in generation to generation changes in alleles as well as a loss in genetic diversity
Founder Effect
A small part of a population is separated from the greater population and begins (founds) a new population. The new population is smaller, and the genetics might not be the same as the greater population
Migration
Individuals who move between populations are introducing new alleles into the gene pools of the new population. This increases genetic diversity in the population but reduces genetic differences between populations
Gene Flow
Genetic exchange due to the migration of fertile individuals or gametes between populations
Mating is not random
There is no way to predict which make would mate with what female. In many animal populations mates are chosen on the basis of their phenotypes. After a while the gene pool will contain more alleles from the alpha male than any other animal
Selection (artificial or natural) is occurring
Within every population there is variation, if one individual is better suited to the environment than another he is more likely to survive and reproduce. After a while the populations gene pool will have changed, a greater proportion of individuals who have the survival trait will be present. In selective breeding only animals with desirable traits are selected for breeding, others do not get bred and the gene pool with change.
Mutations
Are random and unpredictable, when mutations happen they can introduce new alleles and therefore new traits into the gene pool. The frequencies of the old traits decreases with the appearance of a new trait.
H-W Equations
P=frequency of dominant allele (not individuals) Q= frequency of recessive allele (Not individuals) p+q=1 P2=homozygous dominant Q2=homozygous recessive 2pq=heterozygous
