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.

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Blueprint of Life Summary

  • Evidence of evolution suggests that the mechanisms of inheritance, accompanied by selection, allow change over many generations:

  • 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.

Evolution theory:

  • All living species come from preexisting species and that all living things have a common ancestor in some initial form of primitive life.

  • Changes in the environment of living organisms can lead to the evolution of plant and animal species.
  • Changes in the environmental conditions may be physical, such as temperature changes, or chemical, such as changes in water salinity and also competition – for example, competition for resources such as food and water, or competition to reproduce.

Changes in the physical Environment:

  • The Earth has continually changed since life first evolved.
  • Various changes in sea levels, the splitting of the continents and great changes in climate are just some of the environmental changes that life on earth have had to cope with, or become extinct.
  • Changes in the environment force species to either die out, or survive and diversify.

An Example – The Peppered Moth:

  • Prior to the Industrial Revolution, the majority of the peppered moths were light coloured. They survived better as they could camouflage against the white lichen on the trees.
  • Post – revolution, the pollution caused the trees to blacken with soot. The trees could no longer hide white moths. The darker variant of the moth was better able to hide, and so the population of the Peppered moth shifted from mainly white to mainly dark.
  • This is how change in the environment can affect the evolution of an organism.

Changes in the chemical Environment:

  • In the early years of life, the environment on earth was chemically unable to support life as we know it today.
  • However, as organisms evolved special pigments that allowed them to exploit the carbon dioxide in the atmosphere, many organisms appeared.
  • Chemical changes in the environment impact on the evolution of organisms.

An Example – Mosquitoes and DDT:

  • When DDT (dichloro – diphenyl – trichlorethane) was first used as an insecticide to kill malarial mosquitoes, low concentrations were effective.
  • In later doses, higher concentrations were needed and sprayings became less effective.
  • The few DDT – resistant mosquitoes that had survived passed on their genes to their offspring, and now the mosquito population is mainly resistant.

Competition for resources:

  • Competition for resources affects evolution because the survival of a species relies heavily on its ability to obtain the resources needed for life.

An Example – Dinosaurs:

  • When the dinosaurs were the dominant life form on Earth, mammals were very scarce.
  • The Dinosaurs had access to most of the resources and so mammals were unable to reproduce into different niches.
  • When mass extinction of dinosaurs occurred, the mammals quickly diversified to take advantage of all the available resources, such as plants, or other organisms.

  • In essence, competition for resources and changes in the physical and chemical environment influence the evolution of plants and animals.

  •  a first-hand investigation or  from secondary sources (including photographs/ diagrams/models) to observe,  and  the structure of a range of vertebrate forelimbs:

  • The similarities between the different forelimbs of these different vertebrates can be clearly seen
  • They all consist of a forearm bone, connected two a dual lower arm group, connected to wrist bones (carpals in humans) which connect to the digits. Usually 5 in number (pentadactyl).

  • 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.

RECALL:

  • Fossils are any preserved remains or traces of past life found in sedimentary rocks of different ages.

  • Palaeontology: is the study of fossils – provides evidence that living organisms have changed over time.
  • Fossils show a clear change from simple to very complex organisms.
  • This suggests a change over time, which is evidence for evolution.

Transitional Forms:

  • Transitional forms are examples of organisms that indicate the development of one group of organisms from another or from a common ancestor.

Example 1 – Crossopterygian (lobe- fin) fish:

  • Fish that could absorb oxygen from air appeared 400 mya.
  • It is thought that amphibians developed from fish along this line of descent.
  • A special feature is that it had bones in its fins, which suggest it could drag itself on the land.
  • Fish features: scales, fins, gills
  • Amphibian features: lobe – fins, lungs.

Example 2 – Archaeopteryx:

  • This was a small flying dinosaur with feathers.
  • It appeared in the late Jurassic.
  • Shared features with birds and reptiles, suggesting that birds evolved from reptiles.
  • Reptiles features: long- tail, claws, no keel, solid bones, and teeth.
  • Bird features: wish – bone, feathers.

Biogeography:

  • Biogeography is the study of the distribution of living things.
  • Particular types of plants and animals are found in certain continents and not others. For example, the animals and plants of Asia and Australia are very different.

Example – Waratahs:

  • Three genera of Waratahs, distribution spans southern Pacific Ocean.
  • The present day distribution of these closely related species in the eastern parts of Australia, and New Guinea and the Western part of South America suggest that the two regions may have been connected in the past.

Comparative Embryology:

  • Comparative embryology is the study of embryos of different organisms, looking for similarities and differences between them.
  • The similarity between the embryos of different vertebrate species suggests a common ancestry.
  • The embryos of many different vertebrates all have gill pouches at some stage of development.
  • This suggests that these vertebrates evolved from a common aquatic ancestor.

Comparative Anatomy:

  • Comparative Anatomy is the study of the differences and similarities in structure between different organisms. The structures they have in common are evidence of similar inherited characteristics from a common ancestor.

An Example – The Pentadactyl limb:

  • The Pentadactyl limb is a 5 – digit limb.
  • It is a structure of bones that is found in many vertebrates.
  • It is believed that this limb was inherited from an aquatic ancestor.
  • Xylem is found in almost all plants. This suggests a common ancestor.

Biochemistry:

  • Biochemistry is the study of the molecules and chemical reactions of life.
  • Studies of a wide range of animals have found that many possess similar molecules, which is further evidence of common ancestry,
  • Some biochemical processes are the same for all living cells.
  • Certain proteins are commonly found in a large number of organisms.
  • Chemical tests of blood proteins have been used to show biochemical similarities or evolutionary relationships between animals.
  • Closely related species have few differences in DNA. Humans and chimpanzees have only about 1.0% difference in DNA.

  • Explain how Darwin/Wallace’s theory of evolution by natural selection and isolation accounts for divergent and convergent evolution:

Natural Selection:

  • Natural Selection states that those organisms which have characteristics that best suit them to their environment will survive, reproduce and pass some of those characteristics onto their offspring.

  • There are variations within every population of species.
  • Organisms that don’t reproduce have their genes removes from the population.
  • Organisms that survive and reproduce are well suited to their environments.
  • Favourable variations are passed onto offspring and become common.

The Role of Isolation:

  • For a new species to evolve, groups of organisms need to be isolated from each other.
  • Usually the organisms become separated by a physical barrier.
  • Within each separate population, different mutations occur, and therefore, different variations are produced.
  • Natural Selection acts differently on each isolated population, as there are different environmental conditions and selection pressures.
  • Overtime the populations differ so much that they no longer interbreed, and new species will develop.
  • Isolation can be created by a difference in food preference, to the splitting of the continents.

Divergent Evolution: evolving to be different.

  • Also know as adaptive radiation.
  • It is the process that begins with one species and produces organisms that look different from each other because they have evolved from isolated populations in different environments.
  • One of the best known examples are Darwin’s finches.
  • 14 different species were described; all with similar calls, nests, eggs, and courtship displays.
  • However, their habitats, diets, body size and beak sizes were different.
  • Darwin believed that they all evolved from a common ancestor.

Convergent Evolution: evolving to be similar.

  • Natural Selection over many generations can result in similar adaptations in species that live in similar environments. This process is called convergent evolution.
  • For example, the seal and the Dolphin both live in the ocean.
  • They have flippers as limbs, they are strong swimmers, can hold their breath longer than most mammals, and they have a layer of fat under their skin.
  • But they belong to different orders of mammals and are unrelated.
  • Their similarities are the result of evolutionary convergence through natural selection in a similar marine environment.
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  • Use available evidence to analyse, using a named example, how advances in technology have changed scientific thinking about evolutionary relationships:

  • New technologies, especially in the field of biochemistry, have increased knowledge about the relationships between species.
  • Techniques such as DNA hybridisation, amino acid sequencing and analysis of the antibody-antigen reaction between different species have shown the degree of similarity and evolutionary pathways of organisms.

DNA Hybridisation:

  • DNA hybridisation is a process by which the DNA of different species can be compared
  • The process uses heat to separate the 2 strands of the double helix, from ...

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