9.3Blueprint 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 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 closing 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 environments. 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.

This module increases students understanding of the history, nature and practise of biology, the applications and uses of biology, the implications of biology for society and the environment and current issues, research and development in biology.

9.3 – Blueprint of Life:

1. Evidence of evolution suggest 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 the physical conditions in the environment:

–Changes in the chemical condition in the environment:

–Competition for resources:

  • Analyse information from secondary sources to prepare a case study to show how environmental change can lead to changes in a species:

–Evolution is the process of change that occurs in living organisms over many generations. It is a result of natural selectionof favourable characteristics/variations in a species so that the species is more suited to its environment and thus more likely to survive.

–Evolution in a more compartmentalized sense, refers to change of life forms due to changing conditions

–Evolution is the change (evolving) of living things over time – millions of years

–Changes in the environment of living organisms can lead to the evolution of plant and animal species.

–Changes in the Physical Environment:

  • Changes include:

Sea levels

Temperature, wind and amount of rainfall

Splitting of continents

Vegetation (grass, trees – rainforests 50 mya in Australia – now more Eucalyptus trees and bush environments which is subjected towards other animals which are suitable for this environment

Not too much water yet – this changes the prevalence of animals

In a timeline over billions of years,

4 – 4.6 billion years ago = high temp, molten lava – this could not support many life forms

2.3 billion years ago to around 4 – liquid water appears, and temp decreases – oxygen started to appear in the atmosphere, absolutely no oxygen in the atmosphere before – life changes, cellular respiration – using of oxygen and glucose to use ATP. This means our bacteria can use more oxygen to create more energy, grow into complex, variation of species

3.8 – 3.9 billion years ago – water went from gas into liquid form, as soon as liquid water appears and temperature started to decrease, first life – bacteria, very simple bacteria as oppose to complex

50 million years ago – drying up of Australia from a rainforest to more dry eucalyptus, and grassland to support life there – organisms must adapt to this changing environment

  • Example, the Peppered Moth (Biston Betularia): Britain

Prior to the Industrial Revolution of the late 18th Century, there existed 2 main types of moths, the majority of the Peppered moths were light coloured form (with a little brown), whilst the lesser were black. The white moths survived better, ie had a selective advantage as they could camouflage against the white lichen on the trees. The black variety could be more clearly seen by predators i.e. birds, so their overall numbers were low.

Post-revolution, physical changes by the pollution caused the trees to blacken with soot, and as this soot spread, much of the light coloured lichen that grew on trees died off, leaving trees dark. 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.

–Changes in the Chemical Environment:

  • Changes include:

pH levels of water

Soil salinity (not all plants are salt tolerant)

Pesticide/poisons

Atmospheric composition (no oxygen – oxygen as a chemical appeared in the atmosphere which changed a lot i.e. dictated the life forms we see on Earth today)

  • Example, Mosquitoes (Anopheles) and DDT:

When DDT (dichloro-diphenyl-trichloroethane) was first used as an insecticide to kill malarial mosquitoes, low concentrations were effective. (more than 90% died)

In subsequent doses, higher concentrations were needed and the sprayings became less effective.

A select few from the population were naturally DDT-resistant that had survived i.e. around 10%; these then reproduced and passed on their resistance gene to their offspring, as a result the majority of the mosquito population is mainly resistant to DDT

  • Example, Bent grass and heavy toxic metal waste:

In mining areas of Wales, some areas of soil got contaminated by heavy metal waste. The bent grass grew in both the unpolluted and polluted areas.

Over a number of generations, the populations on polluted areas became a whole different species.

–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 – and to continue on, breeding offspring and ensuring the continuity of the species
  • Food – Cane toad, introduced in Australia, so therefore it is competing for food with all native animals > Cane toads take lots of food, and therefore native die out due to the cane toad taking all the food and therefore competition leads to the cane toads prevalence
  • Resources are limited in an environment. The number of offspring produced by organisms is far greater than can be supported in an environment. This causes competetion for survival within species and between differing species.
  • Example, dinosaurs and mammals:

During the Cretaceous(65 mya – before where they were dominant and after when the mammals had the lessened resources and ability to diversify) period, the dinosaurs were dominant life forms on Earth, mammals were very scarce – mammals were rat-like compared to dinosaurs

The dinosaurs had access to most of the resources and so mammals were unable to proliferate.

When the mass extinction of the dinosaurs occurred due to the asteroid/meteorite – 65 mya, the mammals that so scarcely populated the planet quickly diversified to take advantage of all the available resources due to lessened competition, such as plants, or other organisms and continue developing into the large number they are now, evolving into more complex organisms such as tigers, bears and larger animals as a whole

They are now one of the most dominant species on Earth

  • Example, flycatchers (type of bird) and prey:

The leaden flycatcher and the restless flycatcher both feed on similar insects but they feed in different manners.

The leaden flycatcher catches or collects insects from trees. But the restless flycatcher hovers above the ground and emits a call that disturbs insects. It then pounces on the insect and feeds on it.

The ancestors of the flycatcher had feed in a similar manner, but as competition occurred, different species of flycatcher evolved occupying different niches.

Extra case study to show how an environmental change can lead to changes in species - Ancient Kangaroo (omnivores) and Modern Kangaroo (Herbivores)

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  • Modern kangaroo is herbivorous – it eats plants, shrubs, grass etc… - it has well developed molar teeth, but their incisor teeth are not as well developed
  • Ancient Kangaroo (omnivores – eat plants + animals – insects and other animals) – they adapt to this lifestyle 25mya, incisor teeth were well developed, which allowed them to eat their food better which was some plants but mostly insects and plants as well
  • 25mya, Australia was mostly rainforest – insects + small animals, plants are less nutritious – the Ancient kangaroo needed to adapt to this environment
  • Variation existed – some differences in all species – some may have well developed incisor teeth and some may have well developed molar teeth – even 25mya
  • The ones that had better developed incisor teeth had a survival advantage, as that helped them to have a nutritious diet, killing insects and small animals better
  • Today, Australia became a lot drier –the food availability changed – lots more grass and bushland and less insects + small animals
  • Incisor teeth – less likely to survive due to less animals + insects to eat
  • Well-developed molar teeth allows effective grass eating, which makes them pass this favourable feature onto their offspring and therefore they have a survival advantage over the Ancient kangaroo who have less developed incisor teeth and are not able to eat grass and plants well
  • Describe, using specific examples, how the theory of evolution is supported by the following areas of study:

–Palaeontology; including fossils that have been considered to be transitional forms:

–Biogeography:

–Comparative embryology:

–Comparative anatomy:

–Biochemistry:

–Evolution cannot be proved, it is a theory in which cannot be experimented, this is because evolution occurs over a million of years, however it can be supported by an array of evidence, including:

–Palaeontology:

  • Palaeontologyis the study of fossils, which are traces of paste life, fossils found in rocks lower down are older than fossils found closer to the surface (unless folding has occurred).
  • Majorityof our fossils are now to 500 million years ago
  • Hard shells make good fossils
  • Before the Cambrian period – most of the animals were bacteria and bacteria doesn’t have a hard shell
  • The Cambrian Period is the first geological time period of the Palaeozoic Era (the “time of ancient life”). This period lasted about 53 million years and marked a dramatic burst of evolutionary changes in life on Earth, known as the "Cambrian Explosion." Among the animals that evolved during this period were the chordates, animals with a dorsal nerve cord; hard-bodied brachiopods, which resembled clams; and arthropods, ancestors of spiders, insects
  • So when they died, they didn’t leave a fossil which can be utilized today - however they did exist in small amounts, hence why we are able to date life to 3.8 billion years ago – Archaeabacteria
  • Because fossils can be aged, the sequence from the very earliest life to the present can be observed, this is called the fossil record, which show a clear change from simple to very complex organisms we see today, which suggests a change over time, which is evidence of evolution, as the disparity in the orgasms works with accordance to the changing environment of Earth, and they have survived and developed offspring – from simple single-celled bacteria (unicellular) to more complex organisms, with accordance to the changing environment
  • E.g. mammals and birds now – before were mainly dinosaurs – before that were fossils mostly in the sea, which makes sense because most of life came from the sea before it moved onto land
  • Example, Horses:

Early horses (Hyracortherium) were small animals with four toes and a small check span. Fossils have been found of horses(Mesohippus) withmedium size, three toes and intermediate cheek span size. Today the modern horse (Equus) is large with only one toe, and large check span. Fossil record shows that in horses there has been a general trend to large size, reduced of toes and larger check span.

They show how living things have changed over time i.e. evolved over time by dating life up to 3.8 billion years ago – first fossil

–Transitional Forms:

  • Transitional forms are type of fossils, whose features place them between different groups of organisms, that is they are an intermediate between a one group of organisms evolving into another. Proving evolution, examples:
  • Crossopterygian (lobe-fin – bones in its fin) fish,(supports the theory that amphibians evolved from fish – appeared about 400mya):

Fish that could absorb oxygen from air appeared 40 mya

Most other fish had to get their oxygen from dissolved water, this fish could breathe oxygen from the air

It is thought that amphibians developed along this line of descent – amphibians formed from this Crossopterygian

Some even became reptiles

This is known as the ancient ancestor of the vertebras (the back bone – vertebrate)

A special feature is that it had bones in its fins, which suggests it could drag itself on the land – walk on land

The transitional sense with the Crossopterygian fish is that it helped animals move from sea animals living in water, to living on the land, becoming amphibian – reptiles also evolved into bird like and animal like animals

FISH features: scales, fins, gills

AMPHIBIAN features: lobe-fins (ie bones in fins), lungs

  • Archaeopteryx(supports the theory that birds evolved from reptiles):

This was a small flying dinosaur with feathers, its fossil is 150 million years old.

It appeared in the late Jurassic

It shared features with both birds and reptiles, suggesting that birds evolved from these reptiles

REPTILE features: long-tail, claws, no keel, solid bones, teeth

BIRD features: Wishbone, feathers, attaches for flight muscles on the sternum (breast bone).

–Biogeography:

  • Biogeography is the study of the geographical distribution of living things (i.e. living things meaning plants and animals).It looks at the pattern of distribution of present-day organisms and fossils from the past.
  • The distribution patterns provide evidence that species have originated from common ancestors and when isolated by physical barriers (i.e. spread of Pangaea – large continent containing all, into Laurasia – Asia + Europe, Gondwana - Australia + South America – now Southern Hemisphere) (preventing interbreeding) have evolved and become new species with often only small differences between them.
  • Australia and Indonesia – not very similar despite small distance – formation of continents preceding this time, as oppose to AU and South America, which evolve similar animals despite the much larger geographical distance because there is a less gap of time in isolation due to Gondwana embodying Australia + South America
  • The environment around them influences their differing adaptations and creates the disparity in their aspects, despite still being similar
  • Their similarities suggest a common ancestor
  • Examples:
  • Waratah:

Three differing but closely related species of Waratah (Telopea) have been found in Australia, Papa New Guinea and South America, suggesting that they each evolved from a common ancestor when they are tied into one as a larger continent i.e. Pangaea or Gondwana – so much time apart, they evolved into different species due to time in isolation by themselves – they evolve with similar structures, but have differences due to the environment they grew up in

The Waratah plants in Asia compared to Australia possess more differences due to the fact that Laurasia wasn’t connected to Australia, as oppose to Gondwana which embodied Australia + South America, they have more similarities despite their geographical difference being much larger, because they were closer together at a closer point in time, as oppose to with every Waratah plant in Pangaea

  • Wallace Line:

When Alfred Wallace was working in Indonesia he noticed differences between the flora and fauna of Bali and Lambok, despite the close distance between the 2 islands.

For example, Bali had birds common to Asian, but Lombok had Australian parrots.

Wallace purposed Wallace’s line, it is hypothetical line between Bali and Lombok marking separation of Australian and Asian faunas. He suggested this change occurred because Australia had separated from Asia before placental mammals(mammals that bear live young) evolved. So, the Australian type had thrived in isolation, whilst those in Asia had been outcompeted by mammals and became extinct.

–Comparative Embryology:

  • Embryology is the study of embryos (early stage of development for eukaryotic organisms) and their development.
  • The embryos of different vertebrates are very similar in their early development – a couple of days old. In fish, amphibians, reptiles, birds and mammals all show the presence of gill slits, tails and muscle blocks.
  • The reason that they have gills in early development i.e. gills in birds or a reptile when it’s not used – further evidence that the common ancestor was the Crossopterygian fish – later development, birds etc… don’t need gills so they go away, but they are still evident in early embryonic development which suggests a common ancestor and a subsequent adaptation to the environment

A bird doesn’t need gills, because it lives on land and derives oxygen from the air not from oxygen contained within water as a fish would do

  • The gill slits develop into:

Gills for fish, external gills for amphibians, for vertebrates no further formation occurs, however for mammals develop into part of the Eustachian tube (an airway that connects the ear with the throat).

  • As for the tail, it develops in fish, amphibians and reptiles but is greatly reduced in birds and humans.
  • The embryos of many different vertebrates is very similar, this suggests that these vertebrates evolved from a common aquatic ancestor.

–Comparative Anatomy: