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Intro&classification

Intro&classification - Biology 5B INTRODUCTION TO...

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The primary course focus is: functional biology of organisms, especially multicellular organisms how organisms are put together and how their structure and physiology let them 'work' in their environments: Structure and function Biology 5B: INTRODUCTION TO ORGANISMAL BIOLOGY Biological diversity and classification In order to make sense of structure and function, we need to deal with biological diversity . Two very important levels of diversity in biology: 1. There are many species of organisms, and they are often very different from each other -- inter specific variation 2. Within species, each individual is different from every other individual -- intra specific variation (intraspecific variation is unique about biology, compared to chemistry or physics) Biological diversity and classification What do we know about diversity (and what don t we know)? We know there are a lot of species -- about 2 million have been described (collected, analyzed, and formally discussed in the scientific literature) Plants ~ 300,000 assorted invertebrates (not arthropods) ~ 100,000 Vertebrates ~ 60,000 (~ 4,500 mammals) Approximate numbers of described species in various groups Arthropods Arthropods > 1,000,000 Insects Insects ~ 900,000 (> 350,000 beetles beetles !) Biological diversity and classification What do we know about diversity (and what don t we know)? We know there are a lot of species -- about 2 million have been described (collected, analyzed, and formally discussed in the scientific literature) We know there are huge differences in form and function between these species. We also know that there are many fundamental commonalities as well (DNA code, sequence similarity, biochemistry, cell structure and function, etc.)
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Biological diversity and classification Example of intra- and interspecific commonalities : DNA sequence difference between any two humans is about 0.1% DNA sequence difference between humans and chimpanzees is about 1% Biological diversity and classification We know that both the commonalities and the differences among species are there because of life’s evolutionary history: descent with modification from shared common ancestors Similar species (like humans and chimpanzees) have recent common ancestors Dissimilar species (like humans and beetles) had common ancestors much farther in the past All species share common ancestry from very long ago (~ 3 - 3.5 billion years ago) -- origin of life Therefore, we organize our knowledge of diversity with a hierarchical system based on evolutionary lineages . This describes common ancestry common ancestry , rather like a geneology or family tree. Biological diversity and classification Phylogenetic relationships -- historical patterns of species formation present past time Phylogeny is often described as a “ tree” as symbolized here: • the ‘trunk' is the most deeply ancestral form the 'branches' are more recent ancestors the green 'leaves' represent existing species the 'dead leaves' represent extinct lineages.
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