Classifying Life's Diversity

Classifying Life's Diversity

• Identifying species relies on three main concepts: morphological, biological, and phylogeny.

Morphological Species Concept

• It uses body shape, size, and structural features to identify species
• This method is widely used, especially for plants
• The main disadvantage is determining how much difference between individuals is too much for them to be called the same species

Biological Species Concept

• It relies on whether two organisms can produce fertile offspring
• This concept cannot be applied in all cases, for instance, when populations are physically separated and unable to interbreed

Phylogeny Species Concept

• This uses the evolutionary history of organisms
• Defining a species as a cluster of organisms distinct from other clusters, related to each other
• Can be applied to extinct species
• A key disadvantage for this concept is when the evolutionary history is not known

Hierarchy of Ranks

• Classifying organisms involves grouping them based on criteria to organize and indicate evolutionary relationships
• Hierarchical classification arranges species in categories from general to specific
• Taxonomic categories are groupings arranged in a hierarchy
• There are levels in the classification scheme known as rank, such as phylum or order
• Each rank's name is called a taxon, ex: phylum Chordata, order Rodentia
• There are 8 ranks in total

Naming Species

• Binomial nomenclature is used, meaning two-part names
• Nomenclature refers to the naming system
• The two-part name is known as the species name
• The first word is the genus name, and the second identifies the particular species
• The scientific name is italicized with the genus capitalized and the species name lowercase, ex: Homo sapiens

Three Species of Evidence

• Anatomical, physiological and DNA evidence help classify
• Anatomical evidence refers to physical characteristics like size, shape, and other features
• Physiological evidence refers to the functioning of organisms, including the proteins they produce
• The proteins a species makes are determined by their genes
• Even similar-looking species may be distantly related due to very different proteins
• DNA evidence refers to similarities in the genetic material that makes up the genes
• Closely related species have similar DNA sequences
• DNA evidence indicates fungi are more closely related to animals than to plants

Phylogenetic Trees

• Scientists use phylogenetic trees to represent hypotheses about evolutionary relationships among groups of organisms
• The roots of the tree represent the oldest ancestral species
• Forks in branches indicate points where ancestral species split, evolved, or changed

Six Kingdoms

• The six kingdoms are Plants, Animals, Protists, Bacteria, Fungi, and Archaea

Two Major Cell Types

• There are two main cell types that are significant for classification at the upper ranks: unicellular and multicellular
• Organisms made up of only 1 cell are described as unicellular
• Organisms made up of more than 1 cell are described as multicellular

Characteristics of the Kingdoms

• Characteristics that distinguish between kingdoms include prokaryotic vs. eukaryotic, number of cells, cell wall material, nutrition, and primary means of reproduction
• Eukaryotes are the only organisms that use sexual reproduction
• An autotroph obtains energy by making its own food, usually using sunlight
• A heterotroph consumes other organisms to obtain energy yielding food

Three Domains

• The three domains are Bacteria, Archaea, and Eukarya
• Genetic and cellular differences between Bacteria and Archaea led scientists to elevate them to the rank of Domain
• All four kingdoms found in the Eukarya domain are eukaryotic organisms
• Organisms in Bacteria and Archaea are unicellular
• Both unicellular and multicellular organisms occur in the Eukarya domain

Types of Diversity

• Species, genetic, and ecosystems

Species Diversity

• Species diversity is the variety and abundance of species in a given area
• This includes representatives from all six Kingdoms and it is important for healthy ecosystems

Genetic Diversity

• Genetic diversity describes the variety of inherited characteristics within a group
• These characteristics are controlled by genes in the organism's cells
• Variety in the gene pool of a population gives a species a greater chance of survival
• Genetically diverse groups have visible and invisible differences between individuals
• Individuals in groups with no genetic diversity are identical
• Genetic diversity is important because it allows populations to survive changing environmental conditions
• Populations that lack genetic diversity are more susceptible to disease
• If none of the individuals within a population have the ability to survive the disease, the entire population could be eliminated

Ecosystem Diversity

• Ecosystem diversity describes the variety of ecosystems found on Earth
• Ecosystems differ in biotic and abiotic factors, and in size

Human Impact on Biodiversity

• Ecosystem Services are the benefits experienced by all organisms in a sustainable ecosystem
• Humans often cause changes to ecosystems in order to increase the ecosystem services
• Many of these changes reduce biodiversity, but some increase it
• Herbicides in agriculture control weeds, increase food production, but decrease biodiversity
• Rainwater carrying herbicides into rivers/lakes can reduce biodiversity in those ecosystems

Prokaryotes vs. Eukaryotes

• Prokaryotic cells are the most ancient cells
• Prokaryotic cells are smaller and simpler, lacking a membrane-bound nucleus
• Eukaryotic cells means “true nucleus"
• These are larger, complex cells with a membrane-bound nucleus

Viruses

• Viruses are structures containing strands of DNA or RNA surrounded by a protective protein coat
• Viruses differ from both prokaryotic and eukaryotic cells
• Viruses are functionally dependent on cells
• They cannot live independently outside of cells; they are dormant and must invade cells for survival and reproduction

Virus Structure

• Viruses structurally differ from prokaryotes and eukaryotes
• Viruses have no cytoplasm, membrane-bound organelles, or cell membranes
• Scientists do not consider viruses to be living organisms

Effects of Viruses

• Viruses cause diseases in plants and animals, affecting populations, species, and ecosystems
• Scientists develop vaccines to fight viral infections

Classifying Viruses

• Viruses are classified by size and shape of the capsid, the shape and structure of the virus, the type(s) of the virus, the genome type and method of reproduction

Reproduction in Viruses

• Viruses are not cellular and do not reproduce by cell division
• They undergo replication within a host cell, which can be prokaryotic or eukaryotic
• Viruses use the host cell to produce copies of themselves, then the copies are assembled inside the host cell

Lytic and Lysogenic Cycles

• The replication cycle of a virus is called the lytic cycle
• During the lytic cycle, the virus' genetic material uses the host cell's machinery to make new viruses
• In the lysogenic cycle, the viral DNA becomes part of the host cell's chromosomes
• When this happens, the infected cell permanently has viral genes
• The viral DNA that becomes part of the host chromosome is then referred to as a provirus

Provirus

• A provirus can invade a cell but does not kill it
• The provirus can lie dormant within the host chromosome until it re-activates and continues with the lytic cycle

Viruses and Disease

• In the lytic cycle, newly formed viruses from the host cell usually kill it
• In multicellular hosts, these new viruses infect neighbouring cells, causing damage
• In viruses undergoing the lysogenic cycle, the effect on the host may not be immediate
• HIV is an example of a retrovirus, containing reverse transcriptase
• It causes the host cell to copy the viral RNA into DNA
• The viral DNA enters the chromosomes of the host cell, becoming a provirus
• Every descendant of the host cell carries a copy of the provirus in its chromosomes
• This can continue for years with no harm to the host
• It becomes difficult to detect because the virus is part of the host chromosomes
• At any time, the provirus can separate from the host chromosomes and complete the lytic cycle

Replication of Viruses

• The herpes simplex virus, for example, causes cold sores in humans
• The sores appear when the viral cycle destroys cells and disappear when the virus is in its provirus stage
• The trigger that causes the switch between phases is unknown

Prions

• Prions are infectious particles that damage the nervous system in the brain, consisting mostly of a single protein
• Discovered in the 1980s, prions are proteins normally found in the body and they are the only known disease-causing agents that lack RNA or DNA
• Diseases result when prions convert from their normal form into harmful particles with the same chemical composition but a different molecular shape

Viruses and Biotechnology

• Researchers insert a gene they want copied into the genetic material of a virus
• The virus then enters a host cell and diverts the cell to make multiple copies of the virus
• Each new virus contains the added gene that the researchers want copied

Bacteria, Archaea, Protists

• The bacteria example is Staphylococcus
• The bacterial cell type is prokaryotic
• The bacteria's cell number is unicellular
• The cell wall material is peptidoglycan
• Bacteria get nutrition through autotroph and heterotroph
• The primary means of bacterial reproduction is asexual
• The archaea example is Sulfolobus Archaea
• The archaeal cell type is prokaryote
• The archaeal number of cells is unicellular
• Archaea cell wall material is not peptidoglycan, occasionally no cell wall
• Nutrition can be through autotrophs and heterotrophs
• The archaeal primary means of reproduction is asexual
• The protists example is Amoeba
• The protists cell type is eukaryote
• The protists number of cells is unicellular and multicellular
• The protists cell wall material is cellulose in some, other times no cell wall
• Nutrition can be autotrophs and heterotrophs
• The primary means of reproduction is asexual and sexual

Theory of Endosymbiosis

• Eukaryotic cells represent the merger of two or more simpler cells, possibly prokaryotic-like
• One cell engulfs a different type of cell
• The engulfed cell survives and becomes an internal part of the engulfing cell
• Membrane-bound organelles in eukaryotes are ancestors of once free living prokaryotes
• Chloroplasts and mitochondria may have been free-living prokaryotes engulfed by larger prokaryotes, performing cellular activities while surviving and serving the host cell

Plants

• Gymnosperms vs. Angiosperms
• Seeds allow plants to reproduce sexually without water, providing protection against harsh environmental conditions
• Seed plants have a life cycle adapted to a terrestrial environment

Gymnosperms

• Conifers are the largest group of gymnosperms
• These are avascular plants with non-enclosed seeds
• They have well-developed vascular tissue that extends from the roots through the stem to needle-like leaves
• Gymnosperms produce seeds exposed on the surface of cone scales
• Cone is a gymnosperm structure that contains male or female reproductive parts
• Male cones are usually soft and short-lived, while female cones are had and long looting

Angiosperms

• Vascular plant with seeds enclosed in protective tissue fruits
• Commonly known as flowering plants
• The flower is an angiosperm structure specialized for sexual reproduction
• Petals attract pollinators, and the ovary develops into a fruit that aids seed dispersal
• The fruit is a mature ovary of a flower protecting and dispersing dormant seeds
• Angiosperms provide food for animals and often contain male and female parts

Angiosperm Classification

• Angiosperms classify as monocots or dicots
• A cotyledon is a seed leaf within the embryo of a seed
• Corn, orchid, and onion are examples of monocots
• Dandelions, crab apples, and maple trees are examples of dicots

Obtaining Nutrients

• Animals get nutrients through Heterotroph
• Plants get nutrients through Autotroph
• Fungi get nutrients through Heterotroph
• Protists get nutrients through Autotrophs and Heterotrophs
• Bacteria get nutrients through Autotrophs and Heterotrophs
• Archaea get nutrients through Autotrophs and Heterotrophs

Biodiversity Crisis

• Threat of climate change and its impact on food sources, habitat changes, reproduction cycles, pollination, and aquatic ecosystems
• Caribou and reindeer populations are dropping drastically, 60% lower in 30 years, due to a lack of food
• Foraging is reduced due to warmer winters and summers with more rain, meaning there are fewer lichens and they are harder to reach
• Earlier springs mean plants are less nutritious by the time the migraine animals arrive in the area

Distribution of Reproduction

• In many species, including the tuatara and the Ontario turtles, environmental temperatures determine the sex of the offspring. Warmer temperatures mean there is an imbalance in male-female ratios

Pollination Failure

• Both animal pollinators and plants may start seasonal growth and development earlier due to warmer temperatures, but their growth cycles may no longer match
• Results in less pollen for the animal forager, which in turn leads to fewer animal foragers, ultimately leading to a decrease in population

Habitat Decline

• Snow-bed plant communications on mountain tops are adapted for flowering in the summer and surviving the winter snow
• Their habitat is lessened as plants living below them are moving up to the warming mountain tops
• This leads to smaller populations of snow-bed plants and less genetic diversity

Aquatic Ecosystems

• Invertebrate growth rate is increased, but population density is decreased, male-to-female ratio changes in some species
• The appetite and feeding patterns of some species are altered
• Fish growth rate decreases and fish consume more oxygen