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Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
Saltation, as proposed by Hugo de Vries, is a theory of evolution that suggests rapid and significant evolutionary change can occur through sudden, large-scale mutations. In this theory, de Vries proposed that new species could arise abruptly from such mutations, rather than through gradual accumulation of small changes over time, as suggested by Charles Darwin's theory of natural selection. These sudden mutations, according to de Vries, could result in the appearance of entirely new characteristics or traits in an organism, leading to the emergence of distinct species. This concept of saltation contrasts with the gradualism proposed by Darwin, where evolutionary change occurs slowly and continuously through the accumulation of small variations over generations.
Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
The discovery of the coelacanth in 1938 off the coast of South Africa was highly significant in the evolutionary history of vertebrates for several reasons:
Living Fossil: The coelacanth is often referred to as a "living fossil" because it was thought to have gone extinct around 66 million years ago, during the Late Cretaceous period. Its discovery alive challenged the long-standing assumption that coelacanths were extinct, providing a remarkable example of a species that has survived virtually unchanged for millions of years. This sheds light on the evolutionary history and persistence of certain lineages over vast stretches of geological time.
Transitional Fossil: Coelacanths belong to a group of lobe-finned fishes called Sarcopterygii, which are considered to be the closest living relatives of tetrapods, the group that includes amphibians, reptiles, birds, and mammals. As such, coelacanths offer valuable insights into the evolutionary transition from aquatic fish-like ancestors to terrestrial tetrapods. Their anatomical features, such as robust limb-like fins and a unique hinge-like structure in the skull, provide clues about the evolutionary adaptations that occurred during this transition.
Evolutionary Conservation: The discovery of the coelacanth highlighted the importance of studying "living fossils" and other ancient lineages to understand evolutionary processes, biodiversity, and conservation. Coelacanths are considered a flagship species for marine conservation efforts, as they inhabit deep-sea environments and are vulnerable to threats such as habitat destruction, pollution, and overfishing.
Overall, the discovery of the coelacanth in 1938 was a landmark event in evolutionary biology, reshaping our understanding of vertebrate evolution and highlighting the significance of studying both extant and extinct species to unravel the complexities of life's evolutionary history.
Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
The common ancestor of the great apes (including chimpanzees, gorillas, orangutans, and bonobos) and humans is believed to be a species of hominid that lived millions of years ago. This common ancestor is thought to have existed in Africa, and while its specific identity remains uncertain, it is typically referred to as a member of the hominin lineage. Hominins are a group of primates that includes modern humans and their extinct relatives, such as Australopithecus and various species of the genusHomo. The exact species that represents the common ancestor of great apes and humans is a subject of ongoing research and debate in the field of paleoanthropology.
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Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
Hugo de Vries' mutation theory and Charles Darwin's theory of natural selection are both significant concepts in evolutionary biology, but they differ in their mechanisms and explanations for how species evolve:
Mutation Theory by Hugo de Vries:
Darwin's Theory of Natural Selection:
In summary, the main difference between de Vries' mutation theory and Darwin's theory of natural selection lies in their proposed mechanisms of evolution. De Vries emphasized the importance of sudden mutations as the driving force of evolutionary change, while Darwin focused on gradual adaptation through natural selection acting on existing variation within populations.
Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
The Hardy-Weinberg equation, \( p^2 + 2pq + q^2 = 1 \), describes the distribution of alleles and genotype frequencies in a population that is not evolving. Here's what each term conveys:
- \( p^2 \): Represents the frequency of the homozygous dominant genotype in the population, where \( p \) represents the frequency of the dominant allele.
- \( 2pq \): Represents the frequency of the heterozygous genotype in the population, where \( q \) represents the frequency of the recessive allele.
- \( q^2 \): Represents the frequency of the homozygous recessive genotype in the population.
- 1: Represents the total frequency of alleles in the population, which is considered constant and equals 1 or 100%.
This equation is derived from the Hardy-Weinberg principle, which states that in the absence of evolutionary forces such as natural selection, genetic drift, mutation, and gene flow, allele and genotype frequencies in a population will remain constant from generation to generation. Therefore, the equation serves as a null hypothesis against which observed genotype frequencies can be compared to detect deviations from expected frequencies, indicating the presence of evolutionary forces acting on the population.
Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
A species becomes founders when a small group of individuals from that species establishes a new population in a previously unoccupied or isolated habitat. The founder effect occurs when this founding population is genetically different from the original population due to the limited genetic variation present in the founding individuals.
Founder events can occur in various scenarios, such as:
Colonization of new habitats: When a small group of individuals migrates to a new and isolated area, such as an island or a newly formed habitat, they become the founders of a new population.
Population bottleneck: A severe reduction in population size, often due to natural disasters, environmental changes, or human activities, can lead to a small group of individuals becoming the founders of a population that subsequently recovers and expands.
Human migration: Human populations can also experience founder effects when small groups of individuals migrate to new regions and establish new settlements.
In all these cases, the genetic composition of the founding population may not be representative of the original population, leading to differences in allele frequencies and genetic diversity. Over time, genetic drift and natural selection may further shape the genetic makeup of the population, resulting in the founder effect.
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Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
According to Hardy-Weinberg's principle, the allele frequency of a population remains constant under certain conditions, such as no mutation, no migration, random mating, infinite population size, and no natural selection. Any change in allele frequency indicates that one or more of these conditions are not being met.
read lessAnswered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
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Answered on 06 Apr Learn Unit 3-Biology and Human Welfare
Sadika
Key concepts about the mechanism of biological evolution/speciation:
(i) De Vries: Saltation or sudden large mutations lead to speciation.
(ii) Darwin: Evolution occurs through natural selection, where individuals with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring.
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