Systematics and Phylogeny Quiz

Systematics and Phylogeny

• Systematics classifies organisms and determines evolutionary relationships.
• Phylogeny is the evolutionary history of a species or group of species.
• Systematists use fossil, molecular, and genetic data to infer relationships.
• A clade includes a common ancestor and all descendants.

Phylogenetic Trees

• A phylogenetic tree represents a hypothesis about evolutionary relationships.
• Each branch point represents the divergence of two species.
• Sister taxa share an immediate common ancestor.
• A rooted tree includes a branch representing the last common ancestor of all taxa.
• A polytomy is a branch where more than two groups emerge.

What Phylogenetic Trees Show

• They show patterns of descent.
• They do not indicate when species evolved or the amount of genetic change in a lineage.
• It’s incorrect to assume that a taxon evolved from the taxon next to it.
• Phylogeny provides information about similar characteristics in closely related species.

Biosphere and Taxonomy

• The biosphere includes all areas of Earth with life.
• An ecosystem consists of living and non-living components.
• A community is the different species in an ecosystem.
• A population is all individuals of a species in a given area.
• Organisms are the individuals of a population.

Levels of Organization

• Organ systems have specialized functions.
• Organs are structures with specialized functions.
• Tissues are composed of cells, the fundamental units of life.
• Organelles are structures within cells with specialized functions.
• Molecules are made up of atoms that can join to form larger structures.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotes lack a membrane-bound nucleus and organelles.
• Eukaryotes have a membrane-bound nucleus and organelles like mitochondria and chloroplasts.
• Prokaryotes have a small cell size.
• Eukaryotes have a larger cell size.
• Prokaryotes have peptidoglycans in their cell wall (bacteria).
• Eukaryotes lack peptidoglycans in their cell wall.

Animal Cells

• The plasma membrane controls what enters and exits the cell.
• Lysosomes contain enzymes for digesting organic particles.
• Mitochondria produce ATP by cellular respiration.
• Ribosomes produce proteins.
• The endomembrane system includes the endoplasmic reticulum and Golgi apparatus.
• The rough endoplasmic reticulum (RER) is involved in protein transport.
• The smooth endoplasmic reticulum (SER) participates in detoxification and steroid production.
• The Golgi processes and packages material for export or use within the cell.
• The nuclear envelope encloses the genetic material and controls entry and exit.
• The nucleolus is involved in the synthesis of ribosomes and RNA.

Three Domain System

• Early classification recognized two kingdoms: plants and animals.
• Later, five kingdoms were recognized: Monera, Protista, Plantae, Fungi, and Animalia.
• The three-domain system (Bacteria, Archaea, and Eukarya) is now widely accepted.

Mechanisms of Evolution

• Gene flow involves the movement of alleles among populations.
• Natural selection leads to differential survival and reproduction based on environmental influences.
• Genetic drift involves random changes in allele frequencies due to chance factors.

Gene Flow

• Gene flow reduces differences between populations over time.
• It is more likely than mutation to directly alter allele frequencies.

Genetic Drift

• Smaller sample sizes have a higher chance of deviating from predicted results.
• Genetic drift causes unpredictable fluctuations in allele frequencies.
• It tends to reduce genetic variation by eliminating alleles.

Founder Effect

• A few individuals become isolated from a larger population.
• Allele frequencies in the small founder population may differ from the parent population.

Bottleneck Effect

• A sudden reduction in population size occurs due to environmental changes.
• The resulting gene pool may no longer reflect the original population.
• Small populations are susceptible to further genetic drift.