Taxonomy and PhylogenyTaxonomy is the branch of biology that produces a formal classification system...
Transcript of Taxonomy and PhylogenyTaxonomy is the branch of biology that produces a formal classification system...
How many species are there?Assumptions:
• Humans can agree on how to define a species…
— biological
— geographical
— molecular
• The murky definition of a species can be
applied to asexual microbes…
Scientists’ best guess…
• There are 8.7 million +/- 1.3 million extant eukaryotic species
• 1.2 million have been classified• 14% of land species (86% undiscovered)
• 9% of marine species (91% undiscovered)• Remember, estimates are that somewhere between 25-200 species go extinct
every day – Holocene Mass Extinction
• Estimates of the number of extant prokaryotic species range from millions to 10,000,000,000,000 (10 trillion)(1 per second = 317,098 years)
• Estimates are that 99% of all species that ever lived are currently extinct
• That would mean up to 1 quadrillion species have existed (1,000,000,000,000,000)(1 per second = 31,709,792 years)
Taxonomy is the branch of biology that produces a formal classification
system for organisms.
Taxonomy was first formalized by Swedish botanist Carolus
Linnaeus in 1735.
His system divided organisms into plants and animals based
on a hierarchical system.
A taxon (pl. taxa) is a category that contains related
organisms.
Taxa are subdivided from broadest (most inclusive) to
narrowest (least inclusive) groups.
The most specific classification is a species.
Each species is given an unique name denoted by both its genus and species.
Names are often based in Latin or Greek, but not always…
The genus is always capitalized, the species is not capitalized.
Genus-species is always italicized or underlined.
The genus can be abbreviated by using the first letter and a period and then the species written out.
Loxodonta africana L. cyclotis Wockia chewbacca
Two primary benefits:
1. minimizes communication confusion amongst scientists
2. provides clues to evolutionary relatedness
Describe a neko…
Levels of Classification
Domain
Kingdom
Phylum
Genus
Species
Class
Family
Order
Eukarya
Animilia
Chordata
Mammilia
Carnivora
Alopex
Canidae
lagopus
Alopex lagopus
Arctic Fox
*Honors
Additional Taxa
Additional levels are often used in order to be more
precise; these are denoted by prefixes and suffixes.
super and infra denote a level above
– e.g. infraclass or superfamily
sub indicates a level below
– e.g. subspecies
Tribe is an additional taxon falling between family
and genus. It is often used in plants and insects, but
is also used in primate classification.
Eukarya KingdomsProtista – heterotrophic or autotrophic (photosynthesis only),
single celled and/or communal, most aquatic; e.g. protozoans,
algae
Fungi – multicellular, absorptive heterotrophs, chitin cell walls
Plantae – multicellular, autotrophic, photosynthesis,
cellulose cell walls
Animalia – multicellular, ingestive heterotrophs, most motile
Determining Evolutionary Relationships
Modern Taxonomy (also sometimes called systematics) relies primarily on the following:
-- Comparative morphology
Compares structures between species
-- Comparative embryology
Compares development of embryos
-- Comparative biochemistry
Compares proteins (amino acid sequences) and nucleic acid sequences (RNA and DNA)
-- Comparative cytology
Compares number, type, and shape of chromosomes
**note the commonality: COMPARE
Comparative Morphology – homologous structures
These are all tetrapods, descended from a
common ancestor.
Analogous structures are not homologous structures…
analogous structure: similar function, different structure; not shared by common ancestor
Cladistics Terms
character – any feature used to
study variation within and
among species; can be
morphological, chromosomal,
or molecular (in this class, we
will focus on morphological)
ancestral character – the
character state that was present
in the most recent common
ancestor of the taxon (also
called primitive character)
derived character – all other
contrasting versions of the
ancestral character
IMPORTANT: These are relative terms! They only work when used together.
Cladogram
clade (Gr. klados, branch) –
fundamental unit of grouping species;
comprises an ancestral linage and all
species descended from that linage.
All members of a clade will share a
derived characteristic.
Nesting multiple clades creates a
cladogram that shows evolutionary
relationships.
**For the purposes in this class, cladogram and phylogenic tree are used interchangeably.
Genus Homo
In zoology, “human” is defined as any animal
within the genus Homo.
The exact path of evolution of this genus is still
being worked out.
Current information indicates it evolved about
2.3 million years ago and, so far, scientists
have identified 7 species of human.
Homo erectusAfrica and Asia
1.89 mya-143,000 ya
Homo rudolfensisAfrica
1.9-1.8 mya
Homo floresiensisIndonesia
100,000-50,000 ya
Homo sapiensGlobally
300,000-present
(has 2-5% neanderthal DNA in non-African lineage)
Homo heidelbergensisAfrica, Europe, Asia
700,000-200,000 ya
Homo habilisAfrica
2.4-1.4 mya
Homo neaderthalensisEurope and Asia
400,000-40,000 ya