Key Terms and Concepts for General Biology: Taxonomy, Evolution, and Animal Diversity

Overview of Key Terms in General Biology

This study guide summarizes essential terms and concepts related to taxonomy, evolution, and animal diversity. Understanding these terms will help you grasp the major characteristics of biological classification and evolutionary relationships among organisms.

Taxonomy and Classification

Taxonomic Hierarchy

Taxonomy is the science of classifying living organisms. The taxonomic hierarchy organizes life from the most general to the most specific categories:

• Kingdom

• Phylum

• Class

• Order

• Family

• Genus

• Species

Example: Humans are classified as Animalia (Kingdom), Chordata (Phylum), Mammalia (Class), Primates (Order), Hominidae (Family), Homo (Genus), Homo sapiens (Species).

Key Taxonomic Terms

• Clade: A group of organisms that includes a common ancestor and all its descendants.

• Taxon (taxa): Any group or rank in a biological classification (e.g., phylum, class).

• Phylogenies: Evolutionary histories and relationships among species or groups.

• Phylogenetic trees: Diagrams that depict evolutionary relationships.

• Monophyletic: A group containing an ancestor and all its descendants.

• Paraphyletic: A group containing an ancestor and some, but not all, descendants.

• Polyphyletic: A group that does not include the most recent common ancestor.

Evolutionary Concepts

Mechanisms and Patterns of Evolution

• Divergent evolution: When two species evolve in different directions from a common ancestor.

• Convergent evolution: When unrelated species evolve similar traits independently.

• Homology: Similarity due to shared ancestry (e.g., vertebrate limbs).

• Analogy: Similarity due to convergent evolution, not common ancestry (e.g., wings of birds and insects).

• Orthologous genes: Genes in different species that evolved from a common ancestral gene by speciation.

• Paralogous genes: Genes related by duplication within a genome.

• Maximum parsimony: The simplest explanation or pathway is preferred in constructing phylogenetic trees.

Genetic and Developmental Terms

• Hox genes: Genes that control the body plan of an embryo along the head-tail axis.

• Mutation: A change in the DNA sequence.

• Endosymbiosis: Theory that certain organelles (e.g., mitochondria) originated as symbiotic bacteria.

Animal Body Plans and Development

Symmetry and Germ Layers

• Radial symmetry: Symmetry around a central axis (e.g., jellyfish).

• Bilateral symmetry: Symmetry with a single plane dividing the body into left and right halves (e.g., humans).

• Gastrulation: Early embryonic process forming germ layers.

• Mesoderm: The middle germ layer in animal embryos, giving rise to muscles and other organs.

Body Cavities

• Coelom: A fluid-filled body cavity completely lined by mesoderm.

• Coelomate: Animals with a true coelom.

• Diploblastic: Animals with two germ layers (ectoderm and endoderm).

• Triploblastic: Animals with three germ layers (ectoderm, mesoderm, endoderm).

Developmental Patterns

• Budding: Asexual reproduction where a new organism grows from the body of the parent.

• Binary fission: Asexual reproduction by division into two equal parts.

• Viviparous: Animals that give birth to live young.

• Oviparous: Animals that lay eggs.

• Ovoviviparous: Animals whose eggs develop inside the mother's body and hatch there or immediately after laying.

• Cephalization: The concentration of sensory organs and nervous tissue at the anterior end (head) of the body.

• Metamorphosis: A developmental process involving a dramatic change in body form (e.g., caterpillar to butterfly).

Animal Diversity and Feeding Strategies

Major Animal Groups

• Vertebrates: Animals with a backbone.

• Invertebrates: Animals without a backbone.

• Filter feeders: Animals that obtain food by filtering small particles from water.

• Predators: Animals that hunt and consume other organisms.

• Scavengers: Animals that consume dead organisms.

• Parasites: Organisms that live on or in a host and obtain nutrients at the host's expense.

• Heterotrophic: Organisms that obtain energy by consuming other organisms.

• Endoderm: The innermost germ layer, forming the lining of the digestive tract and other internal organs.

• Ectoderm: The outermost germ layer, forming skin and nervous system.

Summary Table: Key Terms and Their Functions

Term	Definition/Function
Clade	Group of organisms with a common ancestor and all its descendants
Homology	Similarity due to shared ancestry
Analogy	Similarity due to convergent evolution
Coelom	Body cavity lined by mesoderm
Viviparous	Gives birth to live young
Oviparous	Lays eggs
Metamorphosis	Developmental change in body form
Filter feeders	Obtain food by filtering particles from water

Additional info: Some terms (e.g., 'maximum parsimony', 'Hox genes', 'endosymbiosis') are advanced concepts in evolutionary biology and developmental biology, included here for completeness and context.