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Alfred Wallace
Independently published a similar theory to Darwin, based on his observations in Indonesia. However, Darwin was credited with the better theory as he had more evidence compared to Wallace. Darwin had developed his theory 15 years before publishing, however the theory is often referred to as the Darwin/Wallace Theory of Evolution by Natural Selection due to Wallace's contribution
Theory of Evolution big ideas
The theory of evolution states that life forms on earth have genetically changed with time. Different species have gradually developed in response to changing environments. These changes have usually occurred slowly over millions of years
Over time species have not remained constant – they have changed. New species have arisen and others have become extinct
There has been a general change of simple to more complex forms of life
Evidence for evolution
Fossil Evidence
Comparative Embryology
Comparative Anatomy
Biogeography
Biochemical Evidence
How do fossils support the theory of evolution?
Provides a record of the development of species that once existed over time
Evolutionary stages can be represented by a change in the species physical appearance in fossils over a long period of time (gradual change)
Examples of fossil evidence supporting the theory of evolution
Vertebrates: the chronological appearance of different vertebrates in the fossil record is supported by other types of animals
Early species of fish had no legs, but developed them in their transition to land, creating amphibians. Amphibians would turn into reptiles, reptiles to birds and so on
All occuring from 500mya to 150mya
Transitional species: an intermediate species between two different species. The theory that organisms develop from each other or a common ancestor is supported by many transitional forms
Archaeopteryx who has the features of both a reptile and a bird
Relative Dating
Involves looking at which layer of sedimentary rock a fossil is found in. Comparisons can be made to nearby rocks of the same type
Absolute Dating
Uses the proportion of radioactive isotopes to quantitatively determine the age of a rock/fossil (C-14 dating, Argon-argon dating)
Comparative Embryology
The science of observing similarities and differences in the structure of vertebrate embryos at different stages of development
How does comparative embryology support the theory of evolution?
Suggests species had a common ancestor, by their embryos being similar in structure in very early stages in life
The more alike the embryos at later stages of development, the more closely related the species
Examples of comparative embryology supporting the theory of evolution
Shark, lizard, chicken, pig and human embryos are similar in structure, having gill slits, a tail and notochord in early developement
Comparative anatomy similarities
Modern day vertebrates have a similar ‘basic’ structure of their vertebrate forelimbs called homologous structures
A human, cat, whale, bat, bird, lizard and frog each share the same five part structures in their arms
Comparative anatomy differences
The common ancestor to these species was likely isolated in different environments, and have adapted over time to form new species as a result of different selection pressures
Each species uses its vertebrate forelimb for a different purpose/environment
Structure reflects function
How does comparative anatomy support the theory of evolution?
Suggests species had a common ancestor, by features of the body being similar in structure
Examples of comparative anatomy supporting the theory of evolution
The presence of a humerus, radius, ulna and phalanges in a range of species (human, frog, lizard, bird, cat, whale, bat). The structure/placement of these bones in these species is the same, however vary in size and shape
Whale comparative anatomy example
Function: Forelimbs act as flippers, heloing it swim easily and stabilise its body and aid in its turns
Structure: The humerous, ulna and radius are shorter and more dense, providing strength in the arm. The phalanges are longer in comparison, to aid steering
Vestigal structures
Structures that have no apparent function and are ‘residual’ organs/structures from a past ancestor
How vestigal structures support the theory of evolution
Provides evidence for evolution as these structures, as they serve no purpose however are present in the organism
It would be wasteful to continue to provide resources to these structures, therefore the environment tends to favour those with reduced versions or without these structures
Examples of vestigal structures
Wings on flightless birds
Legs on snakes
Human tailbone
Pelvic bone on whale
Biogeography
The study of how plants and animals are geographically distributed on different continents
How does biogeography support the theory of evolution?
Suggests species evolved from a common ancestor when geographically separated, which placed different selection pressures on them, causing them to evolve
Examples of biogeography supporting the theory of evolution
Darwin’s Finches: where the birds beak sizes changed as a result of changing environment and selection pressures, believed to have shared a common ancestor
Flightless birds: different flightless birds are located continents that were once part of Gondwana and are theorised to have a common ancestor (emus, ostriches, cassowary, kiwi)
How does biochemical evidence support the theory of evolution?
Suggests species had a common ancestor, evident in the presence of similar genetic code. The more similar the DNA, the more likely they share a common ancestor
Examples of biochemical evidence supporting the theory of evolution
Structures of amino acid sequences in our DNA. Sequences present in species which have common proteins and in similar sequences will be more closely related
Basic structure of genes and protein
Nucleotides with different bases of adenine (A), thymine (T), cytosine (C) and guanine (G)
The number, types and order of the bases determined what amino acid is produced
The order of amino acids determined the type of polypeptide chain and therefore protein that is produced
Amino acid sequencing
Observing and analysing the similarities in the sequence of amino acids which male up common proteins found in a range of organisms
Example of amino acid sequencing
Cytochrome C: a protein involved respiration that is common to all aerobic organisms from bacteria to plants to animals
Humans and chimpanzees share 100% of their cytochrome C amino acids
Humans and rhesus monkeys share all but one
Less so with dogs, snakes and tuna
Antibiotics
A class of drugs used to treat bacterial infections/diseases
Example of antibiotics
Pencillin - A broad-spectrum antibiotic, first produced by the Pencillium fungi. They work by damaging the bacteria’s cell wall, resulting in a build-up of pressure so it bursts (therefore it cannot reproduce)
Antibiotic Resistant Bacteria
Bacteria that have been able to evolve in response to the use of medicines, meaning they are unable to be treated
How does antibiotic resistant bacteria relate to natural selection/evolution?
Within every population there is variation. Some bacteria will be resistant to antibiotics
When treated with an antibiotic, those that are not resistant will die (antibiotics act as a selection pressure)
These ‘resistant’ bacteria are able to survive and reproduce, passing this ‘resistance’ onto their offspring
Evolution in cane toads
Over time there is has been an increase in leg length for cane toads
Resulting in an increase endurance
Resulting in travelling approximately 0.5 km more per day
In the 1930s they were spreading at approximately 15 km/year, current estimates suggest up to 60 km/year in distribution spread
Comparisons between toads in NT and QLD
Move more, longer, stronger legs, travel at night, physically larger
How do cane toads relate to natural selection/evolution?
Lack of selection pressures enable them to repoduce
Toads with favourable characteristics survive (Larger, longer legs, more toxins)
Has also led to snakes (red belly black snakes) evolving to be able to consume smaller toads with less poison and are more likely to survive to eat more toads