Biology Today (BIOL 109)

Talk Two:Classifying Nature

Chapter Two

Biological classification• Used to group and categorize organisms into groups such

as genus or species. These groups are known as taxa.

• Think about classification that is used in everyday life– What would happen if grocery stores did not use a

classification system?– What about libraries, movie stores, department stores,

etc.?

• About 1.8 million species have been given scientific names– nearly 2/3 of these are insects

• Total number of living species is estimated to be between 13 and 14 million – with most being insects and microscopic life forms in

tropical regions

Biological classification• So with all these things

on the planet how can you learn and understand them?

• Start with the simplest, (Cells), and work upwards!

• Start with similar characteristics and work out how things are different.

• Remember the different levels of organization!– If it wasn’t a big

enough job in the first place!

From the wikimedia free licensed media file repository

Living Things are Alike• Common Characteristics like:• Cells:

Fundamental unit of life is the cell – all

living things are made up of cells.

• Tissues:– Similarly specialized cells that perform a

common function.

• Organs:– Similarly specialized tissues that perform a

common function.

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OH H

CH2OH

Levels ofBiological Organization I

SubatoSubatomicmic ElectronElectronNeutronNeutronProtonProton

NitrogenNitrogenCarbonCarbonHydrogenHydrogen OxygenOxygen

DNADNAGlucoseGlucoseWaterWater

NucleusNucleusChloroplastChloroplastMitochondrionMitochondrion

Nerve CellNerve Cell

AtomicAtomic

MolecularMolecular

OrganelleOrganelle

CellularCellular

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Levels ofBiological Organization II

TissueTissue NervousNervousTissueTissue

BrainBrain

NervousNervousSystemSystem

PronghornPronghornAntelopeAntelope

OrganOrgan

Organ SystemOrgan System

OrganismalOrganismal

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Levels ofBiological Organization

III

PopulationPopulationHerd of PronghornsHerd of Pronghorns

HawkHawk

WaterWater

Earth’sEarth’ssurfacesurface

CommunityCommunity

EcosystemEcosystem

BiosphereBiosphere

PronghornsPronghorns

HawkHawk GrassGrass

PronghornsPronghornsSnakeSnakeBushesBushes

SoilSoilAirAir

SnakeSnake

Biological classification• Modern biological classification has its root in

the work of Carl Linnaeus, who grouped species according to shared physical characteristics. 

• Linnaeus attempted to describe the entire known natural world and gave every species a two-part name.– Linnaeus is often known as “The Father of

Taxonomy”

• These groupings were later revised to improve consistency with the  Darwinian principle of common descent.

• He established that all species of life have descended over time from common ancestors, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.

Carl Linnaeus

Charles Darwin From the wikimedia free

licensed media file repository

Animals diversified in the ocean about 600 million years ago.

Plants colonized land about 440 million years ago and were followed shortly by animals.

Humans of any sort are a very recent evolutionary development (~ 7 million years ago).

Life’s HistoryLife’s History

in the ocean

There are two major types of cells

1. Prokaryotic2. Eukaryotic

• The eukaryotic cell is more complex and contains organelles

• The DNA of a eukaryotic cell is contained in the nucleus

Nucleus(contains

DNA) Eukaryotic cell

Prokaryotic cell

DNA(no nucleus)

Organelles

Figure 6.2Biological Evolution• First true cells were

prokaryotic.– Eukaryotic cells

evolved later, followed by the other kingdoms.

Biological evolution is a change in life forms that has taken place in the past and will take place in the future.

Adaptation is a characteristic that makes an organism able to survive and reproduce in an environment.

Box 6.2 (1)

Box 6.2 (2)

Box 6.2 (3)

Components of a Cell

Components of a Eukaryotic Cell

• Nucleus--contained within a cell by nuclear envelope. The nucleus contains DNA.

• Ribosomes--these structures make protein.• Endoplasmic Reticulum--this is a membrane

network composed RER--rough has ribosomes makes proteins, and SER--smooth makes lipids.

• Golgi Apparatus--modifies proteins involved in secretion.

• Endomembrane system--Composed of nuclear envelope, ER, Golgi, Lysosomes and Vesicles, these organelles all work together to make protein sorting and protein secretion possible.

The Mitochondria • Contain their own DNA and

protein-synthesizing machinery

– Ribosomes, transfer RNAs, nucleotides.

– Thought to have evolved from endosymbiotic bacteria.

– Divide by fusion

– The DNA is in the form of circular chromosomes, like bacteria

– DNA replication is independent from DNA replication in the nucleus

The MitochondriaSite of Cellular Respiration

• This process requires oxygen.• Composed of three stages:

– Glycolysis--glucose splitting, occurs in the cell. Glucose is converted to Pyruvate.

– Krebs cycle--Electrons are removed--carriers are charged and CO2 is produced. This occurs in the mitochondrion.

– Electron transport--electrons are transferred to oxygen. This produces H2O and ATP. Occurs in the mito.

The Chloroplast• Contain their own DNA and

protein-synthesizing machinery

– Ribosomes, transfer RNAs, nucleotides.

– Thought to have evolved from endosymbiotic bacteria.

– Divide by fusion

– The DNA is in the form of circular chromosomes, like bacteria

– DNA replication is independent from DNA replication in the nucleus

The Chloroplast• Membranes contain chlophyll

and it’s associated proteins– Site of photosynthesis

• Have inner & outer membranes

• 3rd membrane system– Thylakoids

• Stack of Thylakoids = Granum

• Surrounded by Stroma– Works like mitochondria

• During photosynthesis, ATP from stroma provide the energy for the production of sugar molecules

3 Domains and 6 Kingdoms

A Closer Look at the Taxa

•As one goes from the Kingdom to the Species (DOWNWARD)…An increase in the similarity between organisms occur.

•There are fewer numbers of different kinds of organisms

From the wikimedia free licensed media file repository

Categories Within Kingdoms

• Kingdoms are divided into groups called phyla

• Phyla are subdivided into classes

• Classes are subdivided into orders

• Orders are subdivided into families

• Families are divided into genera

• Genera contain closely related species

• Species is unique

Human Classification• Kingdom : Animalia (animal in Latin)

• Phylum : Chordata (spinal cord)

• Class : Mammalia (mammary glands)

• Order : Primates (two mammary glands)

• Family : Hominidae (bipedalism)

• Genus : Homo

• Species : sapiens

Classifying Organisms• Phylogenetics – based on common

evolutionary descent

– Phylogeny – a representation of organisms based on and describing evolutionary relationships. It is the cornerstone of a branch of biology called systematic taxonomy.

– Systematics – the study of the evolution of biological diversity

Classifying Organisms cont.

• Phylogeny - based on various evidence, including form and structure (observable traits). Must be based on homologous, not analogous structures

– a. Homologous structures - similarity in structure due to common descent, not reliant on function. E.g. vertebrate forearms: human hand, bat wing, whale fin, cat leg.

– b. Analogous structures - similarity in structure based on adaptation for the same function, not common descent. E.g. wings have developed independently in insects, reptiles, birds, and bats.

Homologous Structures

All have the same bones, but are used in different ways and for various functions –

remember, homologous structures have common ancestry!

Homologous Structures

Analogous Structures

Wings of bat, bird, and insect have the same function, but are not from the same descent

Comparison Between Homology and Analogy

• Phylogenetics is usually based on a combination of these lines of evidence:

– Fossil record

– Morphology

– Embryological patterns of development

– Chromosomes and DNA

– How do you think these lines of evidence help to determine evolutionary relationships?

Fossils

From the wikimedia free licensed media file repository

The formation and early development of living organisms

Embryology

Chromosomes and DNA

Analyze to find links between organisms

One of two groups of prokaryotic organisms, organisms with no nuclear membrane. (Bacteria are the other group.)

Archaea are best known for living in extremely hostile environments (very hot, very acid, or very salty), but they can also be found in less extreme conditions.

Archaea are believed to be the earliest form of life on Earth. Although both archaea and bacteria are simple life-forms, archaea are very different from bacteria.

Archaea do not require sunlight for photosynthesis, as plants do, and they do not need oxygen. Archaea absorb CO2, N2, or H2S and give off methane gas as a waste product.

ArchaeaArchaea

ARCHAEAARCHAEA

BacteriaBacteria – the Most Abundant Organisms

There are more bacteria in your mouth than there have been people living since the dawn of humans.

Bacteria (Staphylococcus aureus; yellow spheres) adhering to nasal cilia.

E. Coli bacteriaBorrelia burgdorferi, the bacterium that causes Lyme disease.

Mycoplasma hyopneumoniae

More Bacteria!

• Don Bryant and David M. Ward, (2007) Science. 317(5837):523-6

• Candidatus Chloracidobacterium thermophilum:

• Aerobic phototrophic Acidobacterium

• New genus and species. It also belongs to the Acidobacteria phylum, a poorly characterized phylum that was not previously known to include bacteria capable of photosynthesis.

• Give the hot springs in Yellowstone their remarkable yellow, orange,

red, brown and green colors. From the wikimedia free licensed

media file repository

The Domain EukaryaEukarya is divided into 4 Kingdoms:

Protista Fungi Plantae Animalia

PROTISTSPROTISTS

• Protists are eukaryotes because they all have a nucleus. • Most have mitochondria. • Many have chloroplasts with which they carry on photosynthesis.

• Many are unicellular and all groups (with one exception) contain some unicellular members.

A better name for Protists would be ""Eukaryotes that are Eukaryotes that are neither Animals, Fungi, neither Animals, Fungi, nor Plants"nor Plants"..

From the wikimedia free licensed media file repository

FUNGIFUNGI

Fungi sometimes look like plants, but they’re not!Fungi can’t photosynthesize, because they don’t have chloroplasts; they get their nutrients from the organic material they live in.

Are Decomposers --feed on dead organic material.

Some fungi feed on living organisms, such as plants, animals and even other fungi. This causes diseases and infections in these organisms (like athlete’s foot and ringworm in humans). Some fungi live as symbiotic partners with algae. The result: lichen

Other differences from plants:• fungi don’t have roots, they have a mycelium.• fungi’s cell walls are made of chitin, not cellulose.

PLANTPLANTSS

No vascular system Vascular system

Mosses, Mosses, Liverworts, Liverworts, HornwortsHornworts

Seedless Plants (reproduce by spores)

Ferns, Ferns, Horsetails, Horsetails, Club MossesClub Mosses

Seed Plants (reproduce by

seeds)

Gymnosperms (“naked seeds”)

Angiosperms (flowers,

seeds enclosed in

fruit)Conifers Conifers Cycads Cycads GingkoesGingkoes

Flowering PlantsFlowering Plants

The Plant Cell wall• Cell walls are held

together by the middle Lamella.

• Made up of:

• Cellulose• Xyloglucan• Pectin• Proteins• Ca ions• Lignin• other ions• Water

The Plant Cell wall• The cell wall is the organelle

that ultimately controls the shape of plant cells and consequently of organs and whole organisms.

• It is sometimes naturally strengthened and made considerably more resistant to such abuses as pathogen infection by the release of specific oligosaccharides and enzymes and by overlaying or impregnation with cutin, suberin, waxes or silica

ANIMALSANIMALS

Invertebrates (no backbone)

Vertebrates (backbone)

Animal ClassificationAnimal Classification

As you can see, we mammalsmammals (4000 species) are far outnumbered by the other vertebrates, or chordatesvertebrates, or chordates (38,300). And vertebratesvertebrates (42,300) are definitely outnumbered by invertebratesinvertebrates (989,700 species). The biggest categories of invertebrates: INSECTS!

Summary• Classification is based on similarities and

evolutionary history

• Prokaryotic cells – Have no organelles– No nucleus – one single chromosome

• Eukaryotic cells– Many organelles– Large complex genome containing many

chromosomes

Summary – and thoughts for the next few weeks

• Biological evolution continues at act today in all species

• Natural selection continues to act today by both differential mortality and differential reproduction

• One frequent result of evolution within species is geographic variation

The end

Any Questions?