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Heredity and Evolution: Meaning of Evolution, Human Evolution, History of Evolutionary Thought
Evolution
Meaning of Evolution
- It is the change in the heritable characteristics of biological populations over successive generations.
- During reproduction, these characteristics are passed on from parent to offspring.
- The process of evolution has given rise to:
- Biodiversity at every level of biological organization.
- Levels of species.
- Individual organisms and molecules.
- Through change sin heritable traits, Evolution in organisms occur.
- For example, eye colour is an inherited characteristic.
- An individual might inherit the “brown-eye trait” from one of their parents.
Charles Darwin
He is also known as the “Father of Evolution” and was an English Naturalist and Biologist.
Evolution of Life
- It is believed that the Prokaryotes inhabited the Earth from approximately 3 – 4 billion years ago.
- Between 1.6 – 2.7 billion years ago, the eukaryotic cells emerged.
- plants and fungi colonised the land and were soon followed by arthropods and other animals about 500 million years ago.
Human Evolution
- Humans belong to the primate family.
- Ancestors of Humans include:
- Dryopithecus
- Ramapithecus
- Australopithecus
- Homo erectus
- Homo sapiens
- Cro-magnon man
History of Evolutionary Thought
Classical Times
One type of organism could descend from another type.
Medieval
All-natural things as actualisations of fixed natural possibilities were considered by Aristotelianism.
Pre-Darwinian
- The Aristotelian approach was rejected by the new method of modern science in the 17th century.
- Explanations of natural phenomena in terms of physical laws.
- The hierarchical nature of species relationships was explicitly recognized by biological classification introduced by Carl Linnaeus in 1735.
Darwinian Revolution
- He believed that population growth would lead to a “struggle for existence” .
- Charles Darwin in 1842 penned the first sketch of the Origin of Species.
Pangenesis and Heredity
- Gregor Mendel in 1865 proposed that the traits were inherited in a predictable manner through:
- Independent assortment.
- Segregation of elements (later known as genes) .
- Most of Darwin՚s pangenesis theory was supplanted by the Mendel՚s laws of inheritance.
The ‘Modern Synthesis’
- It connected natural selection and population genetics in the 1920s and 1930s.
- The patterns observed across species in populations was explained by the modern synthesis.
- Advancements were also made in:
- Phylogenetic systematics.
- Mapping the transition of traits into a comparative and testable framework.
Further Syntheses
The biological phenomena across the full and integrative scale of the biological hierarchy starting from genes to species.
Adaptation
- The process that makes organisms better suited to their habitat.
- It can be further referred to a trait that is important for an organism՚s survival.
- One of the best examples is that of the adaptation of horses՚ teeth to the grinding of grass.
- Adaptation may cause:
- Either the gain of a new feature.
- Or the loss of an ancestral feature.
Coevolution
- Both conflict and cooperation can be produced due to the interactions between organisms.
- In a second species, the evolution of one species causes adaptations.
- Thus, the cycle of selection and response is called coevolution.
- For example, the production of tetrodotoxin in the rough-skinned newt.
Speciation
It is the process where a species diverges into two or more descendant species.