Classification and Clades

2.1 Individuals, populations, communities and ecosystems

HL only

Cladograms

A cladogram is a diagram that shows evolutionary relationships between species.

Look at the cladogram to the right and answer the questions:

1. Which primates are most closely related to humans?
2. Approximately how many years ago did our most recent common ancestor with a tarsier exist
3. Circle the clade that includes gibbens and humans, and their common ancestor.

HL only

Source: Socratic

Classification

We classify living organisms into groups. It allows for efficient identification and prediction of characteristics.

The word “taxon” means “group”. Scientists that classify organisms are called taxonomists. (More on taxonomy later this chapter).

​

RECAP

Classification

HL only

Source: Awkwafaba

Domain

Classification

HL only

Source: Awkwafaba

(notice it is presented bottom to top in this diagram)

Source: CNX OpenStax

Domain

Classification

HL only

Source: Awkwafaba

Source: CNX OpenStax

Domain

We give species a binomial name using the genus and species names. It is written in italics with an uppercase letter for the genus (but not the species.

​

Canis lupus ❌

canis lupus ❌

Canis Lupus ❌

Canis lupus ✅

Classification

All organisms within in one group share a common ancestor.

E.g. if two organism are in the same genus, they have the same common ancestor (along with all other organisms in that genus).

​

HL only

Source: Awkwafaba

Domain

Classification

TASK:

Create a mnemonic to remember the taxa in order from Life to Species.

HL only

Source: Awkwafaba

Domain

Classification

e.g.

Lonely dogs kick people ‘cos of feeling grumpy sometimes.

HL only

Source: Awkwafaba

Domain

The Rock Hyrax

The Rock Hyrax (Procavia capensis) is a mammal native to the middle east and Africa.

Which animal(s) do you predict this shares a common ancestor with?

HL only

Source: Sharp, C. J.

The Rock Hyrax

HL only

Source: Benoit, J et. al.

The Rock Hyrax

TASK:

Using the rock hyrax as an example, outline the challenges in classifying living organisms.

HL only

Source: Benoit, J et. al.

TASK:

Using the rock hyrax as an example, outline the challenges in classifying living organisms.

• Organisms are classified by their evolutionary history.
• The rock hyrax has an appearance similar to a rodent/rabbit but actually shares a more recent common ancestor with sea cows and elephants.
• Organisms of the same groups tend to share characteristics and appear similar, but the rock hyrax shows this is not always true.
• It is often difficult to classify living organisms without in depth analysis (e.g. DNA sequencing)

HL only

Source: Benoit, J et. al.

Bibliography

• Awkwafaba, CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons
• Benoit, Julien et al (2016). New material of Seggeurius amourensis (Paenungulata, Hyracoidea), incluDing a partial skull with intact basicranium. Journal of Vertebrate Paleontology. 36. e1034358. 10.1080/02724634.2015.1034358.
• CNX OpenStax, CC BY 4.0 <https://creativecommons.org/licenses/by/4.0>, via Wikimedia Commons
• Sharp, C. J. - Own work, from Sharp Photography, sharpphotography.co.uk, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=68629436
• Socratic (2017) ‘The DNA of humans and gorillas is about 98 percent identical. What does this say about humans and gorillas?’ Socratic https://socratic.org/questions/the-dna-of-humans-and-gorillas-is-about-98-percent-identical-what-does-this-say- CC BY-NC-SA 4.0