Three Domains Of Life Flashcards
biodiversity
refers to all of the
variety of life that exists on Earth
Taxonomy
-science of classifying
-Classification is an important step in understanding the present diversity and past evolutionary history of life on Earth
Linnaean Classification
oAll modern classification systems have their roots in the Linnaean classification system. It was developed by Swedish botanist Carolus Linnaeus in the 1700s.
oIt consists of a hierarchy of groupings, called taxa.
Unity in the diversity of life
A striking unity underlies the diversity of life; for example,
• Cell is the basic structural and functional unit of all organisms
• DNA is the universal genetic language common to all organisms
o near university of the genetic code provides evidence of the common ancestry of all life
• Unity is evident in many features of cell structure
biological species
-is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with members of other such groups
-Gene flow between populations holds a species together genetically
-based on the potential interbreed not physical similarity
Phylogeny
is the evolutionary history of a species or group of related
species
Sister taxa
are groups that share an immediate common ancestor that is not shared by any other group
phylogenetic tree
-represents a hypothesis about evolutionary relationships
- Each branch point represents the divergence of two evolutionary lineages from a common ancestor
An organism’s evolutionary history is documented in its genome
▪ Comparing nucleic acids (DNA/RNA) or other molecules to infer relatedness is a valuable approach for tracing organisms’ evolutionary history
▪ DNA that codes for rRNA changes relatively slowly and is useful for investigating branching points that diverged hundreds of millions of years ago
▪ Examination of the sequences of the ribosomal ribonucleic acid (rRNA) (the 16s RNA) from different organisms and other characteristics concluded they comprised three phylogenetic domains
3 domains of life
Bacteria(prokaryotes)
Archaea (prokaryotes)
Eukarya
• Prokaryotes were the first organisms to inhabit the Earth
• Prokaryotes thrive almost everywhere, including places too acidic, salty, cold, or hot for most other organisms
-Most are unicellular, although some species form colonies
-Most prokaryotic cells are 0.5–5 μm, much smaller than the 10–100 μm of many
eukaryotic cells
-Prokaryotic cells have a variety of shapes
-The three most common shapes are spheres (cocci), rods (bacilli), and spirals
Bacteria
Most bacterial cell walls contain peptidoglycan, a network of sugar polymers cross-linked by polypeptides
Archaea
• Archaea share certain traits with bacteria and other traits with eukaryotes
• Archaea contain polysaccharides and proteins but lack peptidoglycan
• Some archaea live in extreme environments and are called extremophiles
o Extreme halophiles live in highly saline environments o Extreme thermophiles thrive in very hot environments
Domain Eukarya
• includestheprotistsandthreekingdoms
o Plants, which produce their own food by photosynthesis o Fungi, which absorb nutrients
o Animals, which ingest their food
Protists
• Exhibit more structural and functional diversity than any other group of eukaryotes
• Thesearemostlysingle-celledorganisms
• Some protists are less closely related to other protists than they are
to plants, animals, or fungi
• Some protists reproduce asexually, while others reproduce sexually, or by the sexual processes of meiosis and fertilization
Genome Size
• Genomes of most bacteria and archaea range from 1 to 6 million base pairs (Mb)
• Genomes of archaea are mostly within this size range
• Eukaryotic genomes tend to be larger
• Most plants and animals have genomes greater than 100 Mb; humans have 3,000 Mb
• Within each domain there is no systematic relationship between genome size and phenotype
Number of Genes
• Free-living bacteria and archaea have 1,500 to 7,500 genes
• Unicellular fungi have about 5,000 genes and multicellular eukaryotes up to at least 40,000 genes
• Number of genes is not correlated to genome size
Eukarya: animals
▪ Most animals are composed of cells organized into tissues that have different functions
▪ Tissues make up organs, which together make up organ systems
▪ Some organs, such as the pancreas, belong to more than one organ system
There are four main types of animal tissues:
▪ Epithelial
▪ Connective
▪ Muscle
▪ Nervous
Epithelial tissue
▪ It covers the outside of the body and lines the organs and cavities within the body
▪ It contains cells that are closely joined
▪ The shape of epithelial cells may be cuboidal, columnar, or squamous
▪ The arrangement of epithelial cells may be simple (single cell layer), stratified (multiple tiers of cells), or pseudostratified (a single layer of cells of varying length)
Eg; cuboidal epithelium,simple columnar epithelium,simple squamous epithelium,pseudostratifided columnar epithelium
Connective tissue
Blood
Cartilage
Adipose tissue
Bone
Collagenous fiber
Connective Tissue
▪ Connective tissue mainly binds and supports other tissues
▪ There are three types of connective tissue fibre, all made of protein:
oCollagenous fibres provide strength and flexibility oReticular fibres join connective tissue to adjacent tissues oElastic fibres stretch and snap back to their original length
▪ Connective tissue contains cells, including
oFibroblasts, which secrete the protein of extracellular fibers oMacrophages, which are involved in the immune system
6 types of connective tissue
o Loose connective tissue binds epithelia to underlying tissues and holds organs in place
o Fibrous connective tissue is found in tendons, which attach muscles to bones, and ligaments, which connect bones at joints
o Bone is mineralized and forms the skeleton
o Adipose tissue stores fat for insulation and fuel
o Blood is composed of blood cells and cell fragments in blood plasma o Cartilage is a strong and flexible support material
3 types Muscle tissue
Cardiac
Skeletal
Smooth
Muscle tissue
▪ Muscle tissue is responsible for nearly all types of body movement ▪ Muscle cells consist of filaments of the proteins actin and myosin,
which together enable muscles to contract
▪ Muscle tissue in the vertebrate body is divided into three types:
o Skeletal muscle, or striated muscle, is responsible for voluntary movement
o Smooth muscle is responsible for involuntary body activities o Cardiac muscle is responsible for contraction of the heart
Nervous tissue
-Nervous tissue is the groups of organized cells in the nervous system
—Nervous tissue is grouped into two main categories:
- Neurons,ornerves,transmit electrical impulses
-Glia,orneuroglia,formmyelin,supportandprotectneurons.
Bacteria
▪ Most bacterial cell walls contain peptidoglycan, a network of sugar polymers cross-linked by polypeptides
