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What is directional selection?
What is directional selection?
Provide an example of stabilizing selection.
Provide an example of stabilizing selection.
newborn babies weights
Define Genotype.
Define Genotype.
Genotype is all of the alleles that an organism carries on its chromosomes.
Predation occurs when the predator population falls.
Predation occurs when the predator population falls.
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Conservation is the human management of the Earth's resources and typically involves the managing of ________.
Conservation is the human management of the Earth's resources and typically involves the managing of ________.
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What is meant by Phenotype?
What is meant by Phenotype?
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Match the type of speciation with its cause:
Match the type of speciation with its cause:
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What is the term used for alleles where only a single allele is required for the characteristic to be expressed in the phenotype?
What is the term used for alleles where only a single allele is required for the characteristic to be expressed in the phenotype?
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Codominance is when only one allele is expressed in the phenotype.
Codominance is when only one allele is expressed in the phenotype.
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Sex linkage refers to the expression of an allele dependent on the __________ of the individual.
Sex linkage refers to the expression of an allele dependent on the __________ of the individual.
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Study Notes
Inheritance
- Genotype: all the alleles an organism carries on its chromosomes
- Phenotype: observable characteristics of an organism, result of genotype and environmental factors
- Alleles: alternative forms of a gene
- Locus: specific position of a gene on a chromosome
- Types of alleles:
- Dominant: expressed in phenotype when one or two copies are present
- Recessive: expressed in phenotype when two copies are present
- Codominant: both alleles expressed equally in phenotype
Monohybrid Inheritance
- Studying a single gene trait
- Example: cystic fibrosis, where doubly recessive individuals are affected
- Cross between a pure breeding green podded pea plant (dominant) and a yellow podded pea plant (recessive) results in a 3:1 ratio of dominant to recessive traits in the offspring
Dihybrid Inheritance
- Studying two characteristics at once
- Example: crossing round, yellow seeds (both dominant) with a plant pure breeding for wrinkled, green seeds (both recessive)
- Results in a more complex ratio of traits in the offspring
Codominance and Multiple Alleles
- Codominance: two alleles are expressed equally in the phenotype
- Example: human ABO blood groups, with three alleles (IA, IB, and Io) that lead to different antigens on the surface of red blood cells
- Multiple alleles: more than two alleles for a gene
Sex Linkage
- The expression of an allele dependent on the gender of the individual
- Sex chromosomes: X and Y chromosomes that determine sex
- Females: XX, carry two alleles of sex-linked genes
- Males: XY, carry only one allele of sex-linked genes
- Example: haemophilia, a sex-linked disease that affects males
Autosomal Linkage
- The presence of two or more genes on the same autosomal chromosome
- Example: a cross between two genes, A and B, can result in different combinations of alleles depending on whether they are on the same or different chromosomes
Epistasis
- The interaction of different genes, where one gene affects the expression of another
- Example: two genes in mice that control fur color, with one gene (B) controlling the expression of another gene (A)
Chi-Squared Test
- A statistical test used to establish whether the difference between observed and expected results is due to chance
- Criteria for use: sample size > 20, discrete categories, raw counts only
- Formula: χ² = (observed - expected)² / expected
- Comparison to critical value (p = 0.05) to determine significance
Populations
- A group of organisms of the same species occupying a particular space at a particular time
- Gene pool: total number of alleles present in a population
- Allelic frequency: proportion of a certain allele in a gene pool
- Hardy-Weinberg Equation: used to estimate allele frequencies and detect changes in a population over time
Variation in Phenotype
- Causes of variation: random fertilization, meiosis, mutation, and environmental influences
- Example: two plants with the same alleles for flower color, but one grows in a soil lacking a certain mineral, resulting in a different flower color
Evolution and Natural Selection
- The niche of a species: its role within the environment
- Natural selection: the process by which better-adapted species survive and reproduce
- Increase in variation in genotypes and phenotypes within a population increases the chance of survival in a changing habitat
Types of Selection
- Directional selection: the selection of individuals with advantageous traits in a changing environment
- Stabilizing selection: the preservation of successful characteristics and the reduction of diversity
- Disruptive selection: the favoring of both extremes of a normal distribution
Speciation
- The process by which new species arise
- Causes of speciation: allopatric speciation (physical barrier), sympatric speciation (chromosomal error or reproductive isolation)
Populations in Ecosystems
- An ecosystem: all living organisms and non-living elements in a particular environment
- Distribution and abundance of organisms controlled by biotic and abiotic factors
- Each species has a niche, consisting of its biotic and abiotic interactions with the environment
Variation in Population Size
- Factors affecting population size: abiotic (temperature, light, pH, water, humidity) and biotic factors (competition, predation, disease)
- Carrying capacity: the maximum population size supported by an ecosystem
Competition
- Intraspecific competition: competition between members of the same species
- Interspecific competition: competition between members of different species
- Examples: male robins competing for territory, red and grey squirrels competing for resources
Predation
- The relationship between predators and prey
- Predators affect prey populations, which in turn affect predator populations
- Example: a predator-prey relationship between a predator and its prey, with oscillations in population sizes
Measuring Population Size
- Methods: randomly placed quadrats, quadrats along a belt transect, mark-release-recapture
- Estimating population size using the mark-release-recapture method
Succession
- The change of one community of organisms into another
- Ecosystems are dynamic, with succession occurring over time### Primary Succession
- Occurs in areas previously devoid of life, such as after volcanic eruptions that form a rock surface
- Pioneer species like lichens, adapted to harsh conditions, are the first to colonize the area
- As organisms die, microorganisms decompose them, adding humus and forming soil
- Soil formation makes the environment more suitable for complex organisms
- Over time, the soil becomes richer in minerals, enabling larger plants like shrubs to survive
- Eventually, a climax community is established, a self-sustaining and stable community of organisms
Secondary Succession
- Occurs in previously colonized areas where an existing community has been cleared
- Examples include areas affected by forest fires
- As a soil layer is already present, succession begins at a later stage
Conservation
- Human management of the Earth's resources
- Involves managing succession
- Examples include controlled burning of land to prevent the formation of a climax community
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Description
This quiz covers the fundamentals of genetics, populations, evolution, and ecosystems, including inheritance, genotype, phenotype, and more.
