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What idea did Lamarck's Theory (Acquired Characteristics) outline?
Which theory proposed natural selection as the mechanism for how new species arise?
What is the main concept behind Genetic Drift?
change in frequencies of alleles due to random events in a small breeding population
Adaptations are the result of a process of gradual, accumulative changes that help an organism survive and ____.
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What is disruptive selection?
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What is sympatric speciation?
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Match the genetic variation term with its correct definition:
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What is artificial selection?
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What is the key piece of evidence for vestigial structures?
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Homologous structures originate from the same common ancestor.
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Who proposed the theory of natural selection?
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Mutations are a source of the ______ variation, and thus the evolutionary factor.
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Match the theorist with their contribution:
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Study Notes
Characteristics of Lamarck's Theory (Acquired Characteristics)
- Outlined the idea that species change over time
- Compared current species of animals to fossil forms and observed what he interpreted as the "line of descent"
- Thought species increased in complexity over time, until they achieved perfection
- Hypothesized that organisms would become progressively better adapted to their environments
- Inheritance of acquired characteristics: the idea that characteristics acquired during an organism's lifetime can be passed on to its offspring
- Example: giraffes have long necks due to their continuous stretching to reach food in higher areas – the new baby giraffe would have a longer neck like their parents
- Noted that an organism's adaptations to the environment resulted in characteristics that could be inherited by offspring
Characteristics of Darwin's Theory (Natural Selection)
- Mapped the coast of South America and explored the natural history of countries and geographical locations
- Theory of evolution by natural selection: explains how life has changed, and continues to change, during Earth's history
- The theory showed populations of individual species became better adapted to their local environment
- The theory proposes natural selection as the mechanism for how new species arise from ancestral species in response to the local environment
- Summary of his ideas:
- Organisms produce more offspring than can survive – eventually, compete for resources
- Individuals of a population vary extensively; variation is heritable
- Individuals that are better suited to local conditions survive to produce more offspring
- Processes for change are slow and gradual
Genetic Drift (Bottleneck Effect, Founder Effect)
- Genetic Drift: change in frequencies of alleles due to random events in a small breeding population
- Smaller the population, the less likely it is that the parent gene pool will be reflected in the next generation
- Failure of a few individuals to reproduce intensifies the effects of genetic drift
- Example: light pink (aa) and heterozygous roses (Aa) did not reproduce; therefore, the allele for light pink petals is lost
- Founder Effect: founders (individuals that form new populations) carry some but not all of the alleles from the original population's gene pool and are not typical of the population they came from
- Inevitably, gene pool is reduced
- Bottleneck Effect: if a population is quickly reduced by starvation, disease, or natural catastrophe, the surviving population only has a fraction of alleles that were present before population declined
- Gene pool will have lost its diversity and allele frequencies will have changed
Adaptations
- Adaptation: result of a process of gradual, accumulative changes that will help an organism survive and reproduce
- Changes are a result of random, heritable mutations in DNA that accumulate over generations
- Give some organisms within a species a better chance of survival than those without the adaptations
- Survival advantage allows those organisms to reproduce and pass the adaptations
Homologous vs. Analogous Traits, Vestigial Features
- Homologous Structures: have similar structure and origin but have different functions
- Originate from same common ancestor
- Example: forelimbs in vertebrates and mammalian hairs
- Analogous Structures: don't have common ancestor but have similar functions
- Provide evidence for adaptation to suit the environment
- Example: fins of a porpoise and a fish
- Vestigial Structures: reduced versions of what were once functional structures in an ancestral species
- Key piece of evidence is a fossil record that shows the once-functional use of a present-day vestigial structure
Theorists
- John Ray (1627-1705)
- First scientist to carry out empirical studies on the natural world
- Developed a classification system for plants and animals
- George-Louis Leclerc, Comte de Buffon (1707-1788)
- First people to publicly challenge the idea that life forms are unchanging
- Speculated Earth was 6000+ years old
- George Cuvier (1769-1832)
- Found the field of paleontology (study of fossils)
- Discovered each layer of rock held a unique group of fossils
- Discovered that oldest fossils are in deepest layer
- Suggested that catastrophic events killed many species (catastrophism) and corresponded to the boundaries between the fossil strata
- Charles Lyell (1797-1875)
- Rejected Cuvier's theory of catastrophism
- Proposed theory of uniformitarianism: geological processes in the past operate at the same rate today
- Suggested that a slow and continuous process could result in substantial changes long-term
- Jean-Baptiste Lamarck (1744-1829)
- Proposed a "line of descent" progression between current species and fossil forms
- Suggested species increased the complexity and became better adapted to their environment over time
- Proposed the idea of the inheritance of acquired characteristics whereby characteristics acquired during an organism's lifetime could be passed on to offspring
Prezygotic Mechanisms
Prevention of Mating
- Behavioural Isolation: signals or behaviours that prevent breeding with closely related species
- Example: Eastern meadowlark and Western meadowlark - habits overlap and difference in songs; therefore, they don't mate
- Temporal Isolation: two species may occupy the same habitat but have timing barriers
- Example: Tropical Orchids - three types live in the same area but flower at different times
- Ecological/Habitat Isolation: two species live in the same general region but different habitats; therefore, do not encounter each other
- Example: Common garter snake and Northwest garter snake - live in the same area but one lives in meadows and the other near water
Prevention of Fertilization
- Mechanical Isolation: two closely related species attempt to mate but are unsuccessful due to anatomical incompatibility
- Example: genitals of some insects have a lock-and-key system
- Gamete Isolation: gametes from two different species may meet but do not fuse to form a zygote
- Example: sperm of one species does not survive in the environment of the female reproductive tract of another species
Postzygotic Mechanisms
Prevention of Hybrids
- Hybrid Breakdown: original two-species cross produces viable and fertile offspring but mating HYBRIDS can't produce viable and fertile offspring
- Example: different species of cotton plant - produce weak and sterile seeds
- Hybrid Inviability: genetic incompatibility of the interbred species may stop development of the hybrid zygote
- Example: Goat and Sheep - embryos die in early development due to dysfunctional mitosis
- Hybrid Sterility (Infertility): hybrid offspring is sterile, representing a reproductive barrier
- Example: Female horses and Male donkey - produce offspring (mules) that are sterile due to dysfunctional meiosis
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Description
This quiz covers the key concepts of Lamarck's theory, including the idea of species change over time, fossil comparisons, and the concept of acquired characteristics. Learn about the inheritance of acquired traits and how species adapt to their environments.
