1.2 Concept And Uses Of Classification Systems
🚀 State why organisms are classified into groups?
Organisms are classified into groups by the features they share.
🚀 Explain the relationship between classification and evolution?
Classification systems aim to reflect evolutionary relationships; organisms that share more features are thought to share a more recent common ancestor.
Describe what is meant by the term species?
A group of organisms that can reproduce; to produce fertile offspring.
Explain why a horse and a donkey are not the same species?
They produce offspring (mule) that is infertile/cannot reproduce; organisms of the same species must produce fertile offspring.
Describe the binomial system of naming organisms?
An internationally agreed system; the scientific name is made up of two parts; the first part is the genus and the second part is the species.
State one advantage of using the binomial system?
It is internationally agreed/understood, so scientists worldwide can identify the same organism without confusion caused by different common names.
Define the term dichotomous key?
A series of paired/two-choice questions used to identify organisms based on observable features.
Describe one rule to follow when constructing a dichotomous key?
Each question/step must offer exactly two choices; based on observable/identifiable features.
Explain why features used in a dichotomous key should be precise?
Vague features (e.g. "large") are subjective and could be interpreted differently; precise features (e.g. "has six legs") ensure the organism is correctly identified every time.
🚀 Explain how DNA base sequences are used to classify organisms?
The sequences of bases in DNA can be compared between organisms; organisms with more similar base sequences are more closely related/share a more recent common ancestor.
🚀 Explain why two closely related species have more similar DNA than two distantly related species?
Closely related species share a more recent common ancestor; they have had less time for mutations to occur and change the base sequence; distantly related species diverged longer ago, so more differences have accumulated.
🚀 Suggest why DNA comparison may be more reliable than comparing physical features for classification?
Physical features can be similar due to adaptation to similar environments rather than shared ancestry; DNA provides direct evidence of evolutionary/genetic relationships.