Everything Life Sciences Grade 10

Deductive reasoning to understand the past DUMMY

Deductive reasoning combines the use of evidence and theories to make deductions about

the past. Therefore scientists use their understanding of continental drift and natural selection

theories, together with evidence of climate changes and extinct organisms from the fossil

record, to piece together Earth’s history.

• Scientists use the fossil record to make conclusions about the history of life through a
  process ofdeductive reasoning.


• Deductive reasoning involves combining our understanding of known principles to
  make conclusions about new evidence that we have uncovered.


• Our knowledge of the history of life is not based on radiometric dating methods alone.
  Rather, through our understanding of the changes in Earth’s climate and biogeography
  allow us to make conclusions about newly discovered fossil evidence.


• For example, our knowledge of the changes to the Earth’s early atmosphere we know
  that the formation of the ozone layer blocked off the damaging rays of the sun’s UV
  rays. This led to the growth of plant species which gradually made terrestrial existence
  possible.


• A transitional fossil is any fossilised remains that is common to an ancestral life form
  as well as to the group that is derived from it.


• It gives us information about how an ancestral species evolved to form the existing
  species.


• An example of a transitional fossil is theArchaeopteryx. It is thought to belong to the
  genus of Theropod dinosaur which is closely related to the birds.

The exercise below requires you to understand the similarities between theArchaeopteryx

and the modern bird.

Activity: Comparing the skeleton of a modern bird to the Archaeopteryx

Aim:

To compare the skeletons of a modern bird (chicken) and Archaeopteryx

Instructions:

1. Use the pictures below to compare the skeletons of a dinosaur (Theropod) , Ar-
   chaeopteryxand a chicken (modern bird).


2. In your answer, give four differences and four similarities betweenArchaeopteryxand
   dinosaurs, and between Archaeopteryxand birds.

322 11.2. Representations of life’s history