Category: Biology

What is Evolution?

There are three important concepts within Evolutionary Biology:

  1. The definition of evolution (common ancestry and descent with modification),
  2. The patterns of evolutionary relationships (depicted as phylogenetic trees or cladograms),
  3. The processes of evolutionary change (for example, natural selection and genetic drift).

A general definition of Evolution is “change over time”, and when used in biology (the study of living organisms), it usually refers to what can be called Biological Evolution – which is about the change over time of living organisms; scientists have been investigating the diversity of life for many years, and their explanation is called “The theory of Evolution”.

In science, a theory is not the same as a hypothesis (a proposed explanation that needs to be tested), a theory is the best explanation of the observations, given the evidence. Since Charles Darwin first proposed evolution more than 100 years ago, scientists have conducted hundreds of thousands of experiments in an effort to refine what we know about the process of evolution; each day we learn something new because evolution involves many different fields of study, including biology, chemistry, geology, and genetics..

Common ancestry forms the core of evolutionary biology. The processes and patterns represent the frontiers of evolutionary biology, where current research yields new discoveries and increases our understanding of the how descent with modification occurs, how species change over time, and how new species form. This information is presented in charts, and depending on which field of study, it is given a different name.

Scientists use the concept of common ancestry to can make and test predictions – for instance, by collecting evidence about the physical appearance of chromosomes as well as the sequence of DNA, biologists found excellent support for the hypothesis that during the course of evolution, human chromosome 2 formed through the fusion of two pre-existing chromosomes. Through careful examination they were able to identify these chromosomes the same that are in other great apes. This is part of the evidence that gives strong support of Common Descent, while at the same time providing strong evidence about the common ancestry shared by Modern Humans and other great apes.

Evolution accounts for the striking patterns of similarities and differences among living things over time and across habitats through the action of biological processes such as natural selection, mutation, symbiosis, gene transfer, and genetic drift – and we’ll get in these in later posts!


How & Where did life start on Earth?

For the past 50 years, scientists have asked the question “how did life begin?” Some start from the present, moving backwards in time to lifes’ simpler ancestors. Others start from the formation of Earth, 4.55 billion years ago, exploring how different chemicals might have  organized to become living things. It’s a question science is still looking at, and however you look at it, it’s all fascinating!

Looking for the oldest fossils of a living thing, palaeontologists have found fossils of microbes dating back at least 3.4 billion years, with older rocks suggesting that organisms were able to use photosynthesis (convert carbon dioxide in to other elements, like sugars, by using sun light) up to 3.7 billion years ago!

Currently, all free-living life uses information carried in DNA as a kind of Construction Foreman – instructing cells to do certain things at particular times; experiments suggest that early life didn’t use DNA, but used RNA, which later evolved in to DNA as more complex life evolved. Scientists are now running experiments in which RNA-based cells may be able to reproduce and evolve.

Scientists have been able to create the building blocks needed for life to arise; They ran an electric current through a mix of ammonia, methane, and other gases believed at the time to have been present on early Earth. They found that they could produce amino acids and other important building blocks of life. Since the first of these experiments, science has takes in new information and with the latest experiments that were conducted with this in mind, the results were basically the same.

But just WHERE did these building blocks come together!? Based on the evidence we have, scientists think that they either came together in places such as:

  • the scalding hot, mineral-rich waters streaming out of deep-sea hydrothermal vents, or
  • Tidal pools or oceans covered by glaciers.

Amazingly, we’re coming to learn that objects like comets and meteorites may have delivered compounds from outer space! NASA and the European Space Agency have launched probes that will visit comets, narrowing down the possible ingredients that might have been showered on early Earth.