BLUEPRINT OF LIFE
CONTEXTUAL OUTLINE:
Because all living things have a finite life span, the survival of each species depends on the ability of individual organisms to reproduce. The continuity of life is assured when the chemical information that defines it is passed on from one generation to the next on the chromosomes.
Modern molecular biology is providing opportunities to alter the information transferred from one generation to the next in technologies such as cloning and in the production of transgenic species.
The segregation and independent assortment of the genetic information within a species provides the variation necessary to produce some individuals with characteristics that better suit them to surviving and reproducing in their environment. Changes in the environment may act on these variations. The identification of mutations and their causes becomes important in preventing mutations and in identifying and potentially nullifying the effects of mutations in living organisms.
Outline the impact on the evolution of plants and animals of:
- changes in physical conditions in the environment
- changes in chemical conditions in the environment
- competition for resources
Things to consider:
- What does outline mean?
- What is the question asking?
- Underline key words
There have been many factors that have impacted on the evolution of plants and animals. The following are some impacts that have altered the evolution of plants and animals:
Changes in chemical conditions in the environment:
Life has been evolving for millions of years. Early earth was an anoxic environment which meant there was no free oxygen. The organisms during the anoxic period metabolised simple organic molecules. A product of this was carbon dioxide. Eventually the build up of carbon dioxide led to the evolution of photosynthetic organisms (plants) that metabolised the carbon dioxide to produce energy and oxygen. This in turn led to the environment changing from anoxic to oxic. This in turn also meant that plants started to evolve according to the environment as well as animals. As more and more plants evolved many more animals evolved due to the food chain.
Other reasons as to how plants/animals evolve:
· DDT
· Antibiotics
Changes in physical conditions in the environment:
The Earth’s conditions are constantly changing. Due to these changes organisms are constantly evolving. The following are some reasons as to why organisms have evolved:
· Sea levels
· Land formations (fossil evidence)
· Meteorite which formed a dust cloud changed the environment (theory)
· Continental drift
· Volcanoes (similar effect as the meteorite)
The above reasons illustrate that organisms must have evolved according to the conditions they faced at the time. Fossil evidence has shown many changes which indicate a change in the environment. One key Australian example is the evolution of the eucalypt. Australia was once covered by lush beech forest. As Australia’s climate changed so to did its vegetation. The soils became drier and the rainfall dropped. This in turn led to the evolution of the eucalypt.
Therefore, it is evident that changes in the physical environment have led to the evolution of plants and animals.
Competition for resources:
Competition for resources usually results in the extinction of a species or a species occupying another niche. There have been many cases whereby competition for resources has led to the evolution of another species. One Australian example is the flycatcher. Due to this species having the same diet there has been diversification of the species. A whole new species has evolved to occupy a different niche. The leaden flycatcher catches its prey around trees while the restless flycatcher catches its prey just above the ground by emitting a call that disturbs the insects. This example shows that if the flycatcher had not evolved, occupying a separate niche, there would have been competition for resources and in turn the species may have become extinct.
Describe, using specific examples, how the theory of evolution is supported by the following areas of study:
- palaeontology, including fossils that have been considered as transitional forms
- biogeography
- comparative embryology
- comparative anatomy
- biochemistry
Things to consider:
- What does describe mean?
- Underline key words
- How would you go about answering this question
Outlined below are specific examples which support the theory of evolution:
Palaeontology, including fossils that have been considered as transitional forms:
Palaeontology, the study of fossils is a specific example that accounts for the theory of evolution. Fossils are formed under strict circumstances and include such traces as bones, teeth, footprints and faeces. There are many reasons as to why fossils aid in the theory of evolution. Firstly fossils can be compared structurally. This can lead to evolutionary relationships and explain an evolutionary pathway. Secondly through carbon dating fossils can be dated as to when they formed/existed. Knowing how old a fossil can determine evolutionary relationships. Thirdly knowing the type of rock the fossil formed in can indicate the time the fossil was formed. Comparing this fossil to another fossil found in the same rock helps scientists make comparisons between the two fossils. Fourthly transitional fossils support the theory of evolution. Archaeopteryx is a transitional fossil that illustrates the relationship between dinosaur’s, reptiles and birds. The lobe fin fish is a transitional fossil that illustrates the evolutionary pathway of fish to amphibians.
Therefore from the above evidence palaeontology supports the theory of evolution as it illustrates evolutionary relationships between organisms.
Biogeography:
Biogeography supports the theory of evolution in many ways. Firstly Darwin and Wallace, through their studies identified that there were striking similarities between current organisms from differing countries. (As well as fossils.) This eventually led to the fact that continental drift affected evolution. This is supported by:
· Pincushion coneflower (South Africa) VS Holly – Leaved Banksia (Australia)
· Opossum in South America and its closest relative in Australia.
The above evidence suggests that these landforms were previously much closer together. Over time these continents drifted apart causing the organisms of that continent to evolve according to its environment.
Comparative embryology:
Comparative embryology supports the theory of evolution. The embryos of the fish, salamander, tortoise, chicken, pig, rabbit and human are all very similar in embryonic stage. These organisms then evolve with each structure having a different specialised function, supporting the theory of evolution.
Comparative anatomy:
Comparative anatomy supports the theory of evolution in a number of ways. It is evident that the fore – limb also known as the pentadactyl limb supports the theory of evolution. The limb has a similar structure in many organisms; however the organism has evolved to use that limb for a specialised function such as swimming or flying.
Biochemistry:
Biochemistry supports the theory of evolution including evolutionary relationships and evolutionary pathways. Virtually all organisms use cytochrome – C, a protein, for energy. Through studies of this protein scientists can compare the similarity between organisms. A change in DNA leads to a different amino acid sequence which in turn produces a different organism. The study of biochemistry therefore supports the theory of evolution.
Explain how Darwin/Wallace’s theory of evolution by natural selection and isolation accounts for divergent evolution and convergent evolution.
Things to consider:
- What does explain mean?
- What is natural selection?
- What is isolation?
- What does account mean?
Background info:
NATURAL SELECTION: is the process by which an organism will adapt to its environment due to natural pressures such as the environment or competition. This leads to desirable characteristics being passed on from one generation to the next. Also known as “survival of the fittest.” e.g. Peppered moths in England.
ISOLATION: is the process by which a group of organisms is isolated from the original species. This new group usually undergoes natural pressures such as environmental change. This leads to mutation and natural selection which in turn produces a new species. e.g. The apple maggot fly and the Hawthorn maggot fly.
ADAPTIVE RADIATION: the process by which an organism adapts to its niche over millions of years.
Darwin and Wallace’s theory of natural selection and isolation accounts for divergent evolution. For example when a species is occupying a certain environment it will be exposed to those environmental pressures. This organism will adapt and continue to evolve over thousands and millions of years, according to these environmental pressures, (natural selection.) However, this same species may become separated or isolated due to flood waters, mountain ranges or even deserts, (isolation.) This then means this organism, due to its new environmental pressures evolves according to its new niche, (natural selection.) Evolution of this species continues to occur until the species become two separate species and are no longer able to reproduce with one another. This is known as divergent evolution. (A species diverges from its original species.)
Darwin and Wallace’s theory of natural selection and isolation accounts for convergent evolution. Convergent evolution is the process by which organisms with different ancestors have acquired the same characteristics according to the similarity of their niche.
Analyse information from secondary sources to prepare a case study to show how an environmental change can lead to changes in a species.
Things to consider:
- What does analyse mean?
- Underline key words
- Ensure you use an example to show how environmental change can lead to changes in the species. e.g. Red kangaroo
A chief example of an environmental change that lead to a change in a species were the peppered moths in England. Peppered moths are either pale in colour or dark in colour. In an unpolluted area the pale moths are well camouflaged by the lichen on the surrounding trees, while the darker moths are much easier to see. The birds within the ecosystem prey on the darker moths as they are much easier to see. This then equates to the paler moths occupying the ecosystem and passing on the desirable characteristic of the pale colour.
However, due to an environmental change the darker moths have flourished. Due to industrial pollution the trees within the area have darkened in colour. Consequently the darker moths have greater camouflage compared to that of the paler moth. This in turn means that paler moths are picked off by the bird population; therefore the darker moths through years of natural selection have a higher survival rate in a polluted area.
TREE COVERED IN LICHEN. (CAN YOU SEE THE PALER MOTH)
TREE AFFECTED BY POLLUTION. NOTE THE DIFFERENCES BETWEEN THE TWO PICTURES.
Perform a first-hand investigation or gather information from secondary sources (including photographs/ diagrams/models) to observe, analyse and compare the structure of a range of vertebrate forelimbs.
Things to consider:
- What does observe, analyse and compare mean?
- Ensure you include diagrams in your research.
ORGANISM / STRUCTURE/FUNCTION / PICTURECrocodile / The crocodile has a short structured forelimb which contains five digits, a humorous, ulna and radius. The forelimb is quite compact with the ulna and radius packed tight together while the humorous is short and quite dense. The angle of the forelimb suggests that the crocodile uses this limb for pushing off, wading in water and walking on land. /
Human / The human forelimb is long in structure. It contains five digits, a humorous, ulna and radius. The humorous is the largest bone. It is thin and long in nature. The ulna and radius are similar in size and structure; they connect to the carpals and phalanges. The human forelimb has many functions including balance. /
Bird / The bird’s forelimb contains a humorous, ulna, radius and three digits. The bones are at different angles suggesting that at rest the forelimb folds up. The density of the humorous, ulna and radius are quite similar. The function of the bird’s forelimb is mainly for flying. /
Bat / The bats forelimb is thin in structure and contains a small humorous, thin ulna, thin radius and five long digits. The angle of the bones suggests that the limb folds up when not in use. The bones are quite thin suggesting that the creature is small and light. The main function of this limb is for flying. /
Whale / The Whales forelimb is very dense in structure. It contains a large square humorous, an ulna, a radius and five digits. Due to the structure of the whale’s forelimb it appears that the whole limb moves as one. Therefore, it is apparent that the main use of the whale’s forelimb is for swimming. /
Frog / The frog’s forelimb contains a humorous, ulna and radius. The humorous is long and thin in structure while the ulna and radius are short and thin in structure. The five digits are long and thin in structure. The function of the forelimb is for balance and to some degree pushing off the ground. /
Use available evidence to analyse, using a named example, how advances in technology have changed scientific thinking about evolutionary relationships.
Things to consider:
- What does analyse mean?
- Ensure you use an example to explain your answer
- Relate your example to evolutionary relationships
One example of an advance in technology that has changed scientific thinking about evolutionary relationships is DNA hybridization. DNA hybridization is used to identify the similarities between two different organisms by comparing their DNA. The process of DNA hybridization is outlined below.
· 2 strands of DNA are collected. One from one species the other from another species.
· These 2 strands are heated which causes the strands to separate.
· One strand from each organism is then combined to form a hybrid. Not all of the bases in each sequence will match up.
· Pairing of the DNA strands depends on the similarities of the organisms being compared. Organisms are said to have come from a recent ancestor if their sequence is highly similar. Conversely if the sequence has a low degree of pairing the organisms are said to unalike.