Speciation Flashcards
Founders Effect definition
When a small group of individuals establishes a new population, leading to a loss of genetic variation compared to the original population.
Bottleneck Effect definition
When in a population undergoes a drastic reduction in size, resulting in a loss of genetic diversity.
Gene pool definition:
The total collection of genes and their alleles present in a population.
Allele frequencies definition:
The proportions of different alleles for a particular gene in a population.
Phenotype definition:
The observable traits of an organism, influenced by both genetics and the environment.
Natural selection definition
Organisms with advantageous traits of survival and reproduction are selected for
Adaptions definition
Traits or features that enhance an organism’s survival and reproduction in its environment,.
Populations definition
Group of individuals of the same species living in the same area and potentially interbreeding.
Species definition
A group of organisms that can interbreed and produce fertile offspring sharing similar characteristics and genetics.
Deme definition
A local population of organisms that interbreed and share a common gene pool within a larger population or species.
Genetic equilibrium:
A state in which the allele frequencies in a population remain constant over generations, indicating that the population is not evolving.
how changes in gene pools have an important effect on alleles of a population including chance effects in small populations
Changes in allele frequencies in small populations can occur due to genetic drift, which involves random fluctuations that have a larger impact when the population is small.
Define allele frequency
is the proportion of a specific allele among all allele copies in a population.
Describe the process of evolution. ( 3 points) (variation. selection, reproduction, and time)
Evolution is the gradual change in living organisms overtime driven by:
- Variation: Within any population of organisms, there’s variation in traits.
Selection: The environment can favour certain traits over others.
- Reproduction: Organisms with traits that help them survive and reproduce tend to pass those traits on to their offspring.
- Time: Evolution takes place over long periods of time, small changes accumulate over generations, leading to significant differences between populations.
Understand the fundamental ideas in Darwin’s “Theory of Evolution by Natural Selection”
Darwin’s theory posits that those possessing advantageous traits for survival and reproduction are more likely to pass on these traits to offspring leading to an increase in the frequency of beneficial traits in the population
Understand the fundamental ideas in modern synthesis
evolution occurs through changes in allele frequencies in populations over time, driven by selection, mutation, gene flow, and genetic drift.
Structural Adaptations:
These adaptations involve physical features or characteristics of an organism’s body structure often that help an organism to survive in its environment.
Behavioural Adaptations:
These adaptations involve actions or behaviours that organisms exhibit to increase their chances of survival or reproduction.
Physiological Adaptations:
These adaptations involve internal biochemical or physiological changes within an organism’s body that enable it to function effectively in its environment. Eg. metabolism
Fitness
refers to how well an organism can survive and reproduce in its environment and and how well-suited its traits are for its environment.
explain how evolution through adaptation equips species for survival and how it works (3 points) (variation, natural selection, and reproduction)
- Variation - Within a species, there’s always variation in traits.
- Natural Selection - Traits that allow organism to survive in environment are selected for.
- Reproduction - Organisms with traits that help them survive and reproduce pass those traits on to their offspring.
Discuss the importance of mutations in terms of evolutionary potential.
fundamental for evolution because they increase variability in populations and thus enable evolutionary change.
Gene flow is the
transfer of alleles between populations through migration and interbreeding.
directional selection:
one extreme phenotype is favored over others, causing the allele frequency to shift in one direction
disruptive selection:
extreme phenotypes at both ends of the spectrum are favored over intermediate phenotypes
stabilising selection:
intermediate phenotypes are favored over extreme ones, leading to reduced variation
Two forms of sexual selection
Contest -
In contest competition, animals directly compete with each other for mates. This could be through fighting.
Sexual selection -
Sexual selection is a process where certain traits in animals make them more attractive to potential mates.
The two forms of sexual selection
Advertising:
In advertising, animals use certain traits or behaviours to attract mates without directly fighting.
Revise how changes in gene pools due to chance effects have an important effect on allele frequencies in small populations: Founders Effect
Occurs when a small group of individuals establishes a new population in a different area. The genetic makeup of this founder group may not represent the original population’s diversity. Over time, genetic drift amplifies certain alleles while eliminating others, shaping the gene pool of the new population.
Revise how changes in gene pools due to chance effects have an important effect on allele frequencies in small populations: Bottleneck effect
In small populations, a drastic reduction in size can lead to a loss of genetic diversity and random changes in allele frequencies due to chance, affecting the gene pool and evolutionary trajectory.
In both cases of the Bottleneck and founders effect, genetic drift leads to changes in allele frequencies due to random chance, rather than natural selection. This can….
reduce genetic diversity and increase the risk of genetic disorders in small populations.
Subspecies:
variations within a species that have distinct characteristics but can still interbreed with other variations of the same species.
Hybrids:
Offspring resulting from the mating of different species or subspecies often a mix of traits from each parent.
Describe the concept of a ring species.
is a group of connected populations that can interbreed with neighboring populations, but the populations at the ends of the ring cannot interbreed, showing gradual evolutionary change around the ring.
Define the term: reproductive isolation
refers to mechanisms that prevent different species or populations from interbreeding and producing fertile offspring
Prezygotic isolating mechanisms happens….
before mating or fertilisation. They include things like differences in behaviour, habitat, or physical traits that prevent mating or fertilisation from occurring.
Postzygotic isolating mechanisms happens…
after mating or fertilisation, but they prevent the hybrid offspring from developing or reproducing. These can include things like hybrid inviability (the hybrid offspring doesn’t survive) or hybrid infertility (the hybrid offspring can’t reproduce).
Isolating mechanisms leading to speciation (2)
Prezygotic mechanisms.
Postzygotic mechanisms
The four aspects of Speciation process
Isolation formation
Genetic divergence
Reproductive
Speciation
Simple explanation: Isolation formation
*isolating mechanisms like habitat preference or behavioural differences, limit interbreeding.
Simple explanation: genetic divergence
In a population of an inbreeding species diverges into two or more descendant species that have become more and more dissimilar in terms of forms and structures.
Simple explanation: reproductive
Over time, genetic differences become substantial mating and reproductive if populations come to into again.
Simple explanation: speciation
Eventually, the populations become so distinct that they are considered separate species.
Allopatric speciation
when a population is geographically separated into isolated groups, leading to genetic divergence and the formation of new species over time due to different environmental pressures and genetic drift.
Sympatric speciation
occurs when new species arise within the same geographic area due to reproductive barriers, without physical separation
Divergent evolution -
wherein a population of an inbreeding species diverges into two or more descendant species that have become more and more dissimilar in terms of forms and structures.
Adaptive radiation
is when a single species quickly evolves into many different forms to adapt to different environments
Convergent evolution definition
unrelated species independently evolve similar traits or adaptations due to facing similar environmental challenges.
Analogous structures:
Similar structures or traits that have a similar function, even when they are not of the same evolutionary origin
Homologous structures:
Traits with similar structures and origins but have different functions, resulting from shared ancestry.
Patterns of species formation:
(4)
-Subsequent evolution
- Divergent evolution
- Coevolution
- Adaptive radiation
subsequent evolution
Gradual transformation of one species into another over time, without branching into new species.
Co evolution definition
where two or more species evolve in response to each other’s adaptations over time.
Punctuated equilibrium
species remain relatively stable for long periods, but experience rapid changes and speciation during brief, intense episodes of environmental change.
Gradualism equilibrium
evolution occurs slowly and steadily over long periods, with gradual changes accumulating to produce new species.
A phylogenetic map is a…..
A phylogenetic map is a diagram that represents evolutionary relationships among organisms.
mtDNA (valuable why? - mutation rates, gene combinations, maternal inheritance, copy number quantity, and accessibility)
a valuable molecular marker for evolutionary relationships due to its high mutation rates, rare gene recombination, maternal inheritance, high copy number, and ease of access.
geographic isolation
species occur in different areas with no geographical overlap.
Ecological isolation
species occupy or exploit different habitats within an area
Behavioural isolation
Different courtship, rituals, sounds, calls or colouration.
Temporal isolation
Activity mating or flowering occurs at different times of the day month or year.
Mechanical isolation
Reproductive structures are incompatible and prevent the delivery or acceptance of gametes.
Gametic isolation
Reproductive structures are incompatible and prevent the delivery or acceptance of gametes.
Postzygotic reproductive mechanisms (3)
- Hybrid inviability
- Hybrid sterility
- Hybrid breakdown
Hybrid inviability
The hybrid embryos are often not viable because the genes of the two species are incompatible and the hybrid dies before birth or before reproductive age.
Hybrid sterility
hybrid offspring that do survive birth and reach sexual maturity are sterile thus cannot produce viable gametes.
Hybrid breakdown
Hybrids viable of producing offspring however these and any subsequent generations harbour detrimental genetic abnormalities
polyploidy creates a genetic barrier that…..
promotes the evolution of new species by preventing interbreeding between polyploidy and non-polyploid individuals within the same population. Decreasing genetic flow between two groups.
polyploidy
a condition where organisms have more than two complete sets of chromosomes, can play a crucial role in speciation.
Formation of Polyploidy Individuals
can occur due to errors in cell division during reproduction, resulting in offspring with extra sets of chromosomes.
Genetic divergence from polyploidy:
Over time, the isolated polyploid population accumulates genetic differences from its non-polyploid counterparts. Without gene flow, these genetic changes can lead to the formation of a new species.
Homologous structures
are body parts in different species that share a common origin but may have different functions, indicating they evolved from a common ancestor.
Analogous structures
structures that have the same function and often appearance but they arose from different origins.
Fossils can reveal (5)
- How organisms changed overtime
- What kind of organisms lived in the past
- What organisms ate
- How organisms moved
- What the climate was like
Disadvantages of fossils (3)
-Gaps in fossil records
-Rare: require unique conditions
-Soft-bodied animals do not fossilise well, therefore method is biassed towards finding organisms with hard parts only.
advantage of fossils
Can provide transitional fossil - fossils showing traits from two different taxonomic groups.
Post zygotic reproductive mechanisms (3)
- Hybrid inviability
- Hybrid sterility
- Hybrid breakdown
Hybrid inviability -
genes of two species not compatible, and hybrid dies before birth or prematurely.
Hybrid sterility
hybrids that reach sexual maturity are sterile.
Hybrid breakdown
offspring produced and future generations harbour detrimental genetic abnormalities resulting in reduced fertility.
Deme
is the subject of a population that has limited gene flow with members of the larger population.
Cline
is a pattern of gradual variation, between individuals, over a geographical area.
List Prezygotic reproductive isolation mechanisms (6) (BEG, GMT)
- Geographic isolation -
- Ecological isolation -
- Behavioural isolation -
- Temporal isolation -
- Mechanical isolation -
- Gametic isolation
Geographic isolation definition
species occur in different areas with no geographical overlap.
Ecological isolation definition
- species occupy or exploit different habitats within an area
Behavioural isolation definition
Different courtship, rituals, sounds, calls or colouration.
Temporal isolation
- Activity mating or flowering occurs at different times of the day month or year.
Mechanical isolation
- Reproductive structures are incompatible and prevent the deliver or acceptance of gametes.
Gametic isolation -
Reproductive structures are incompatible and prevent the delivery or acceptance of gametes.
Genetic drift
random changes in alleles frequencies in a population due to chance events
Bottleneck effect
when a population drastically reduces in size, leading to a loss of genetic diversity
Founder’s effect
when a new population is started by a small group of individuals, leading to reduced genetic diversity and different allele frequencies from the original population.
Gene flow
is the transfer of genetic material between populations through migration and interbreeding
why does genetic drift have a greater impact on smaller populations
because each individual’s alleles make up a larger proportion of the total gene pool.
