A a detailed description of the creature, and an answer to the question of why it is regarded as important evidence for evolution.

Archaeopteryx is the name given to a creature from the Late Jurassic Period (150 million years ago). The characteristics of this animal are strange to the modern eye, as it has a similar body shape to a European Magpie, but has many features in common with Mesozoic dinosaurs, such as the sharp-toothed jaws, clawed fingers, and a long bony tail. This bizarre phenotype has led the archaeopteryx to become a popular example of a transitional fossil, which is closely related to the origin of modern day birds.

Animal Info

The archaeopteryx lived in what is now part of Germany, in an era during which Europe was far closer to the equator, and therefore had a far more tropical climate. The creature would have been 50cm long, and weighed around 0.9 kilograms. It had a lightweight, feathered body, a flat sternum, large eyes, conical teeth (1), a long neck, and long thighs supported by short calves.  Physical data suggests that the creature was capable of flight by this stage, but the ability was far from refined. Despite this, the archaeopteryx’s well developed flight feathers are widely considered the most important part of the fossils, especially in terms of using them as evolutionary evidence, as they have a very similar structure to that of modern birds.

These proto-birds developed over a far longer period than their modern avian counterparts. It is estimated that after hatching, archaeopteryxes took around 32 months to grow to their adult size (all known specimens died and were fossilised as juveniles). They could potentially have lived for up to forty years (2), compared to just twenty years for a contemporary European Magpie (3).

Evolutionary Status

The first archaeopteryx fossil was discovered in 1860, by a German palaeontologist named Christian Erich Hermann von Meyer. The fossil consisted of a single feather, buried in the Solnhofen Limestone of South Germany. The fossil is widely regarded as the first evidence of the archaeopteryx, but little info could be extrapolated from a mere feather, and there is even some uncertainty that the creature it belonged to was even a member of the same species.

In later years, there have been several subsequent discoveries, all far more useful. Detailed analysis has provided strong evidence that the archaeopteryx shows the intermediate evolutionary stage between the Jurassic dinosaurs and modern day birds.

Around the time of their discovery, however, the authenticity of the archaeopteryx fossils was repeatedly questioned. Even as late as 1985, papers were published by physicist Lee Spetner and astronomer Fred Hoyle which set out to prove that the Berlin and London specimens were simply forgeries (4).

The controversy continues to this day, mainly consisting of the anti-evolution arguments perpetuated by religious fundamentalists, but by and large the archaeopteryx fossils have been accepted as solid evidence for the theory of evolution. These fossils are very important to biologists and archaeologists alike because they lay out the ancestral origins of modern-day birds as well as providing a vital clue as to the evolutionary lineage between the organisms of the Jurassic Period and those of the present day. This key position in scientific history has led the archaeopteryx specimens to sit among the most well-known fossils of all time.

1. Confirming that they were carnivores.
2. This is only a vague estimate, as I have found little in the way of precise figures.
3. Both cases assume that the organism lives out its full potential lifespan. Obviously, most would die of unnatural causes long before.
4. Though the reasons given, such as how the slabs of rock around the fossil split so smoothly, merely indicated that they were unfamiliar with lithification (sediments compacting under pressure to become solid rock).

An explanation as to how changes in habitat over millions of years may have caused the modern horse to evolve from an animal no bigger than a fox.

Among the earliest known ancestors of the modern horse (Equus) is Hyracotherium Eohippus, which is believed to have lived around 55 million years ago. The creature was around 60 cm long and weighed 23 kg with four-toed feet and a slender body rather unlike what we would now call a horse. Hyperaesthesia lived in the woodlands of North America and Western Europe during the Eocene era, the hottest period in pre-history. During this time, the ground was mostly soft and moist (particularly in the forest areas), and so the animals were best served by walking with their toes spread out, and their body weight spread evenly between them. This allowed them to walk along soft surfaces without sinking in and becoming stuck.

Eventually the main land became harder and dryer, meaning that the original configuration was no longer necessary (and indeed potentially detrimental). With the ground more stable, the mammals could now run at a much faster pace, so the evolutionary emphasis shifted from buoyancy to power. In order to achieve this, the horses became larger, with their limbs lengthening, and their toes becoming more pointed. With the later generations of the horse now pushing off from one toe, their land speed was dramatically increased, allowing them to more easily outrun predators. There have been other changes, too: with each generation the originally wide-spread toes moved closer together, eventually becoming the now familiar hoof. Meanwhile the teeth changed shape and became more numerous (particularly molars) to keep up with changes in diet.

By the time Homo Sapiens Sapiens developed, the horse had grown to a height of 1.6 metres, and has earned an unofficial title as “Man’s second-best friend” due to their superb pulling and carrying ability making them a vital tool in the formation and development of human civilisation.

A brief summary of what DNA is, with details about its function and discovery.

Deoxyribonucleic acid is a substance which forms the genetic structure of all living organism. DNA is found in the chromosomes contained within the nuclei of living cells, where it is arranged in a double helix structure. The structure is made up of small sections called genes. Each gene helps to control the production of proteins within a cell, and through this they determine the physical characteristics of the organism. The individual strands of DNA are made up of combinations of six different chemicals: Adenine, Thymine, Cytosine, Deoxyribose sugar, Guanine and Phosphate. The chemicals are arranged in nucleotides, with a phosphate molecule first, then a sugar molecule, and then the “base” (adenine, thymine, cytosine, guanine). A DNA strand is formed when two nucleotides lock together. Cytosine is always opposite a guanine nucleotide, because the two molecules are shaped to perfectly lock together, making them “base pairs”. Adenine and thymine are also base pairs. The base pairing rule allows DNA to be replicated when cells divide, because the strands on one helix can have their base pairs made up to match.

Genes determine the phenotype (what the resulting organism will look like). There are often different forms of the same gene (each of which has, for instance, a different eye colour), and these are known as alleles. When a new organism is formed –sexually, it will often inherit two different alleles , one from each parent, but only one allele will be used, while the other remains dormant. We call one allele “dominant” and the other “recessive”. In human eyes, for instance, the allele for brown cornea is dominant to its blue counterpart, so if a person with brown eyes (BB) mates with a person with blue eyes (bb), their child will have brown eyes (Bb). However, if a Bb person mates with a bb person, at least some of their children will have blue eyes again.

As mentioned earlier, DNA molecules are coiled into structures called chromosomes. These consist of one double-stranded DNA molecule tightly coiled around proteins called histones. The number of chromosomes in a cell is different depending on the species. Humans normally have 46, of which there are 22 pairs common to both sexes. The 23rd pair, for females, consists of two X shaped chromosomes, but males have a mismatched pair of one X and one Y shaped. It is this difference which determines a person’s gender. Other species have different numbers of chromosomes: Goats have 60, cats have 38, kangaroos have 16, and snails have 24. The number of chromosomes that an organism has is believed to depend on the number of evolutionary stages which came before its own phenotype.

Occasionally, people can be born with the wrong number of chromosomes. People with Down Syndrome, for instance, have an extra 21st chromosome, and girls with Turner Syndrome are born missing one X chromosome. These birth defects often lead to slowed development, and physical deformities.

DNA as we now know it was first discovered in 1953 by Cambridge University scientists James Watson and Francis Crick. Up until that point, it had been accepted that DNA was the substance which carried genes from one generation to the next, but little was known about what DNA actually was, or how it worked.

Watson and Crick used the research done by Rosalind Franklin, in which she used X-ray diffraction to take pictures of crystalline DNA. Watson and Crick used this research to work out the double helix structure of DNA to match the photographs. Their proposal is now accepted by scientists worldwide. Watson and Crick were awarded the Nobel Prize in 1962, but by then Franklin had died of cancer, and the prize is not allowed to be awarded posthumously.

A description how a leaf and a cell are adapted to ensure that they have a large surface area in relation to their volume and explanation of why they need a large surface area, using diagrams to help.

In order to function efficiently, both a leaf and a cell require a large surface area in relation to their internal volume.

Why cells need surface area

In order for a cell to take in water and nutrients, the substances must defuse through the cell’s membranes. In order to take in a sufficient amount of nutrients, the cell membrane must be made as large as possible. In particular: the surface area must be large enough for the cell’s internal volume. A cell with a large surface area and a small internal volume will be able to take in nutrients more efficiently than one with a small surface area and a large internal volume (1).

How cells ensure a large surface area

A common way in which cells increase their surface area is division: when a cell splits itself in half, the cell’s internal volume remains the same, but the surface area is doubled. The cell can therefore take in nutrients twice as efficiently as before (2).

The surface area of a cell can also be increased by changing the cell’s shape. Having a smooth, spheroid outer layer does not allow for a particularly large surface area. However, if the membrane contains small infoldings, or small bumps/spikes, the surface area is considerably increased (3).

Why leaves need surface area

Whereas cells derive energy through diffusion of nutrients, leaves are fed by beams of sunlight. The more light a leaf absorbs, the more it can photosynthesise and therefore the more food is produced for the plant to which the leaf is attached. A larger plant will thus need larger leaves in order to maintain a sufficient supply of food (4).

How leaves ensure a large surface area

The surface area of a leaf is helped by its shape. Leaves are normally wide, flat and long. This increases the amount of material exposed to direct sunlight, while minimising the leaf’s internal volume (5). Like cells, leaves are often quite rough, because having multiple points which are concave or convex again increases the area. The final method to increase the input of light from leaves is to simply have more of them (6). This is especially useful for plants which grow in confined spaces, and thus lack sufficient room for large leaves, or whose stems are not strong enough to support them.