Genetics and Evolution- Evolution - Divergent Evolution

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Slide 1

• Definition of divergent evolution
• Divergent evolution refers to the process where a single species diverges into two or more different species
• It occurs due to adaptation to different environments or niches
• Example: Darwin’s finches

Slide 2

• Explanation of Darwin’s finches as an example of divergent evolution
• Darwin observed that different species of finches on the Galapagos Islands had different beak shapes and sizes
• The variations in beak morphology were due to adaptation to different food sources available on the islands
• This led to the development of different species of finches

Slide 3

• Factors influencing divergent evolution
• Geographical isolation: Physical barriers can separate populations, leading to limited gene flow and divergence
• Ecological opportunity: New ecological niches can lead to diversification as species adapt to different roles or resources
• Natural selection: Environmental pressures favoring certain traits can lead to divergence

Slide 4

• Role of natural selection in divergent evolution
• Natural selection favors certain traits that provide a selective advantage in a particular environment
• Individuals with these advantageous traits are more likely to survive and reproduce, passing on these traits to future generations
• Over time, populations diverge as different traits become more prevalent

Slide 5

• Adaptive radiation as a form of divergent evolution
• Adaptive radiation occurs when a single ancestral species gives rise to many different species that occupy different ecological niches
• It leads to an increase in species diversity within a relatively short period of time
• Example: Darwin’s finches are considered an example of adaptive radiation

Slide 6

• Homologous structures as evidence of divergent evolution
• Homologous structures are structures that have a similar origin, but may have different functions in different species
• They suggest a common ancestry and provide evidence for divergent evolution
• Example: The pentadactyl limb in mammals

Slide 7

• Analogous structures as evidence of convergent evolution
• Analogous structures are structures that have a similar function, but may have different origins
• They are the result of convergent evolution, where unrelated species independently develop similar traits due to similar environmental pressures
• Example: Wings in birds and bats

Slide 8

• Convergent evolution vs. divergent evolution
• Convergent evolution: Unrelated species develop similar traits due to similar environmental pressures
• Divergent evolution: A single species diverges into two or more different species due to adaptation to different environments or niches
• Both processes can lead to the development of new species

Slide 9

• Evolutionary significance of divergent evolution
• Divergent evolution results in the formation of new species, leading to increased biodiversity
• It allows for the adaptation of species to different niches, increasing their chances of survival
• It provides evidence for the theory of evolution and common ancestry

Slide 10

• Summary
• Divergent evolution refers to the process where a single species diverges into two or more different species
• It occurs due to adaptation to different environments or niches
• Examples of divergent evolution include Darwin’s finches and adaptive radiation
• Homologous structures provide evidence for divergent evolution, while analogous structures suggest convergent evolution

Slide 11

• Examples of divergent evolution in animals
  • Darwin’s finches: Different species of finches with different beak sizes and shapes
  • African elephants vs. Asian elephants: Differences in size, habitat, and tusk shape
  • Anoles lizards: Different species with varying limb lengths based on habitat and perch type
  • Cichlid fish: Different species with variation in mouth shape and feeding habits
• These examples demonstrate how species can diverge and adapt to different environments or niches

Slide 12

• Convergence vs. divergence of traits
  • Convergence: Similar traits evolving independently in unrelated species due to similar environmental pressures
    • Example: Wings in birds, bats, and insects
  • Divergence: Traits of a common ancestor diverging into different forms due to adaptation to different environments or niches
    • Example: Darwin’s finches and their various beak shapes and sizes
• Convergence and divergence are two important evolutionary processes that shape the diversity of life on Earth

Slide 13

• Molecular evidence for divergent evolution
  • DNA sequence comparisons: Species with a more recent common ancestor will have more similar DNA sequences
  • Analyses of genome structures: Comparative genomics can reveal evolutionary relationships and patterns of divergence
    • Evolutionary geneticists can track how genomes have changed and diverged over time
  • Molecular phylogenies: Constructing phylogenetic trees using molecular data can show the degree of relatedness among species
• Molecular evidence provides robust support for the theory of divergent evolution

Slide 14

• Speciation as a result of divergent evolution
  • Speciation is the process by which new species arise from a single ancestral species
  • Divergent evolution plays a crucial role in speciation, as different populations adapt to different environments
  • Over time, these populations accumulate genetic and phenotypic differences, leading to reproductive isolation and the formation of distinct species

Slide 15

• Case study: Darwin’s finches
  • Darwin’s finches are a classic example of divergent evolution
  • The finches on the Galapagos Islands have different beak shapes and sizes, allowing them to specialize in different food sources
  • This variation in beak morphology is a result of adaptation to different environments and resources on the different islands
  • The different finch species have formed as a result of this adaptive radiation

Slide 16

• Effects of divergent evolution on biodiversity
  • Divergent evolution increases biodiversity by generating new species
  • Increased biodiversity can enhance ecosystem resilience and stability
  • Different species occupying various niches contribute to ecological balance and productivity
  • Biodiversity conservation is crucial to maintain these divergent lineages and their roles in ecosystems

Slide 17

• The relationship between divergent evolution and natural selection
  • Divergent evolution is driven by natural selection, as certain traits become more advantageous in specific environments
  • Natural selection acts on genetic variation within a population, favoring traits that improve survival and reproductive success
  • Over time, the accumulation of advantageous traits leads to divergence and the formation of different species

Slide 18

• Human impact on divergent evolution
  • Human activities can influence the process of divergent evolution in several ways
  • Habitat destruction and fragmentation can disrupt gene flow and lead to population isolation, increasing the likelihood of divergence
  • Introduction of invasive species can outcompete native species, leading to changes in ecological niches and potential divergence
  • Climate change can alter environmental conditions, forcing organisms to adapt or face extinction, potentially driving divergent evolution

Slide 19

• Divergent evolution in plants
  • Plants also exhibit divergent evolution, leading to the formation of new species
  • Variation in flower structures, adaptations to different pollinators, and changes in reproductive strategies contribute to plant divergence
  • Examples include the diversity of orchid species or the adaptive radiation of Hawaiian silversword plants

Slide 20

• Recap of divergent evolution
  • Divergent evolution occurs when a single species diverges into two or more different species due to adaptation to different environments or niches
  • Examples include Darwin’s finches, African vs. Asian elephants, and Anoles lizards
  • Molecular evidence, speciation, and effects on biodiversity support the concept of divergent evolution

Genetics and Evolution- Evolution - Divergent Evolution

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Slide 21

• Reproductive isolation and speciation
  • Reproductive isolation occurs when individuals of different populations can no longer mate and produce viable offspring
  • It is an essential component for speciation to occur
  • Reproductive barriers can be prezygotic (before fertilization) or postzygotic (after fertilization)

Slide 22

• Prezygotic reproductive barriers
  • Habitat isolation: Populations are geographically separated and do not come into contact
  • Temporal isolation: Populations have different mating seasons or active times of day
  • Behavioral isolation: Populations have different courtship rituals or behaviors
  • Mechanical isolation: Structural differences prevent successful mating
  • Gametic isolation: Sperm and egg are not compatible

Slide 23

• Postzygotic reproductive barriers
  • Hybrid inviability: Hybrid embryos do not develop or survive
  • Hybrid sterility: Hybrids are sterile and cannot produce viable offspring
  • Hybrid breakdown: Hybrids have reduced fitness or viability over multiple generations

Slide 24

• Sympatric speciation
  • Sympatric speciation occurs when a new species arises within the same geographical area as its parent species
  • It can be triggered by factors such as polyploidy, habitat differentiation, or sexual selection
  • Example: The formation of new plant species through polyploidy

Slide 25

• Adaptive radiation and divergent evolution
  • Adaptive radiation is a rapid diversification of species from a single common ancestor
  • It typically occurs when a new environment or ecological opportunity becomes available
  • Example: The diversification of the Galapagos finches after colonizing different islands

Slide 26

• Allopatric speciation
  • Allopatric speciation occurs when a new species arises due to geographic isolation between populations
  • Geographic barriers prevent gene flow and allow populations to diverge
  • Example: The formation of different species on island chains

Slide 27

• Modes of speciation
  • Allopatric speciation: Geographical isolation leads to divergence and the formation of new species
  • Sympatric speciation: New species arise within the same geographical area, usually due to ecological or reproductive factors
  • Parapatric speciation: Speciation occurs between populations that are geographically close but have limited gene flow due to a habitat gradient

Slide 28

• Examples of divergent evolution in plants
  • Hawaiian silverswords: Over 30 species of silverswords evolved from a single common ancestor, each adapted to different elevations and habitats on the Hawaiian Islands
  • Darwin’s Orchids: Various species of orchids evolved different lengths of nectar spurs, each adapted to specific pollinators
  • Desert cacti: Different species of cacti have adapted to various desert environments, with unique shapes and water storage capabilities

Slide 29

• Evolution and convergent vs. divergent evolution
  • Evolution is the process of change in living organisms over time
  • Convergent evolution and divergent evolution are two types of evolutionary processes
  • Convergent evolution leads to the development of similar traits in different species due to similar environmental pressures
  • Divergent evolution results in the formation of new species from a single common ancestor

Slide 30

• Conclusion

• Divergent evolution is a key mechanism driving biological diversity

• It leads to the formation of new species through the adaptation and divergence of populations

• The process of divergent evolution is influenced by factors such as ecological opportunity, natural selection, and reproductive isolation

• Examples of divergent evolution can be found in various organisms, including plants and animals

• Understanding divergent evolution helps us understand the evolutionary history of organisms and the processes that shape the diversity of life on Earth