Biology Chapter: Organism Classification

Scientific Method and Evolutionary Theory

• Scientific Method involves observation, hypothesis formation, experimentation, data analysis, and conclusion.
• Snowshoe hares use seasonal color molting for camouflage, reducing predation.
• Natural selection is a mechanism where beneficial traits enhance survival and reproduction, increasing their frequency.
• Evidence for evolution includes fossil records, homologous traits, embryology, and molecular data.

Genetic Variation and Speciation

• Sources of variation include mutation, gene flow, genetic drift, and recombination.
• Balancing selection maintains traits like sickle cell allele by providing resistance to malaria.
• Speciation occurs through allopatric (geographic isolation) and sympatric (isolation within populations) mechanisms.
• Pre-zygotic (before fertilization) and post-zygotic (after fertilization) mechanisms prevent reproduction between species, such as temporal isolation or hybrid sterility.

Systematics and Phylogenetics

• Classification organizes life hierarchically (Domain, Kingdom, Phylum, etc.).
• Binomial nomenclature uses unique two-part scientific names for species (e.g., Homo sapiens).
• Phylogenetic trees display evolutionary relationships based on traits (morphological and molecular).
• Cladogenesis and anagenesis represent different patterns of evolutionary change.

Prokaryotes

• Prokaryotes include Bacteria (peptidoglycan walls) and Archaea (ether-linked lipids).
• They lack a nucleus and organelles, with DNA in a nucleoid region.
• Prokaryotes reproduce through binary fission with high mutation rates.
• Horizontal gene transfer occurs via transformation, transduction, and conjugation.
• Metabolic diversity includes photoautotrophs (e.g., cyanobacteria) and chemoheterotrophs (e.g., decomposers).

Protists

• Protists are diverse, including unicellular and multicellular organisms.
• Nutrition can be autotrophic (photosynthesis), heterotrophic (ingesting food), or mixotrophic (both).
• Protists play various roles in the environment, from primary producers (algae) to pathogens (e.g., Plasmodium).
• Examples include Algae, Amoebas

Fungi

• Fungi have cell walls made of chitin.
• Fungi form networks called mycelia for nutrient absorption.
• Fungi are decomposers that break down organic matter and recycle nutrients.
• Reproduction occurs through asexual spores and sexual processes.
• Examples include Mushrooms, Penicillium

Plants

• Plants have alternation of generations between sporophyte (2n) and gametophyte (n) stages, with gametophytes becoming less dominant over evolutionary time.
• Adaptations include cuticles, stomata, vascular tissues (xylem/phloem) and seeds for reproduction.
• Plants classify as nonvascular (bryophytes) or vascular (ferns, gymnosperms, angiosperms).
• They have symbiotic relationships for nutrient absorption and are essential for oxygen production and ecosystem balance

Animals

• Animals exhibit radial (e.g., jellyfish) or bilateral (e.g., mammals) symmetry.
• Animals undergo protostome (mouth first) or deuterostome (anus first) development.
• Major animal groups include basal (sponges, cnidarians), protostomes (flatworms, annelids, mollusks, ecdysozoans) and deuterostomes (echinoderms, chordates).
• Innovations like amniotic eggs to reproduce on land and the development of complex nervous systems are key features of animals.

Summary: Comparing Major Groups

• Prokaryotes: Unicellular, no nucleus, diverse metabolism.
• Protists: Diverse forms, autotrophic/heterotrophic.
• Fungi: Hyphae, decomposers, symbiosis.
• Plants: Photosynthetic, vascular systems.
• Animals: Multicellular, heterotrophic, complex systems.