Biodiversity Conservation Efforts

Mitigating Biodiversity Loss

• IUCN, founded in 1948, promotes global cooperation for nature conservation
• The IUCN created the Red List of Threatened Species in 1964
• The IUCN helped establish international conventions like the CBD and CITES
• CBD, established in 1992, focuses on biodiversity conservation and sustainable use
• CITES, ratified in 1975, regulates international trade of endangered species to prevent extinction
• The International Whaling Commission (IWC), formed in 1946, manages whaling practices and works on whale conservation
• Canada’s Wildlife Act (1985) and the Migratory Bird Treaty Act (1918) protect species by preventing over-hunting and habitat destruction
• The U.S. Endangered Species Act (1973) protects endangered species
• Protected areas conserve biodiversity by providing safe spaces for wildlife
• By 2003, preserves covered 11.5% of Earth's land
• Habitat restoration aims to reverse environmental degradation and improve biodiversity
• The Yellowstone wolf reintroduction (1995) restored ecological balance by controlling elk populations
• Dam removal helps restore free-flowing rivers, benefiting fish species like salmon
• Zoos contribute to conservation through captive breeding programs and education
• Successful breeding programs include the American condor and Whooping Crane reintroduction efforts

Introduction to Evolution

• Biology’s diversity stems from evolution, the process of gradual change in populations over time
• Species diversity results from the balance between speciation (new species formation) and extinction
• Mass extinctions, evidenced by fossils, are periods when over half of species disappeared
• Organisms evolve adaptations to their environments
• Evolution is biology’s unifying theory, explaining species change through natural selection
• Charles Darwin and Alfred Wallace independently developed the theory of natural selection
• Darwin observed species variation, especially finches on the Galapagos Islands
• Darwin published "On the Origin of Species" in 1859
• Divergent evolution: species from a common ancestor evolve different traits
• Convergent evolution: unrelated species evolve similar traits due to environmental pressures
• Natural selection acts on individuals, but species' genotype evolves over long time spans
• Fossils show changes in species over millions of years
• Anatomy shows homologous structures (same structure, different function) and analogous structures (similar function, different origin)
• Vestigial structures are useless remnants of past features
• Species distribution (biogeography) supports evolution
• Species on isolated landmasses evolve uniquely but resemble ancestral mainland species

Phylogenetic Trees

• A phylogenetic tree is a diagram of evolutionary relationships among organisms
• It is based on genetic and physical trait similarities/differences
• Internal nodes represent common ancestors and branches represent evolutionary paths
• Rooted trees have a single common ancestor at the base
• Unrooted trees show relationships without indicating ancestry
• A branch point is where one lineage splits into two (speciation event)
• The basal taxon is an early-diverging lineage
• Sister taxa are two groups that split from the same node
• A polytomy is a node with more than two branches (uncertain relationships)
• Carl Woese’s tree, based on ribosomal RNA sequences, shows 3 domains: Bacteria, Archaea, and Eukarya
• Bacteria and Archaea are prokaryotes
• Phylogenetic tree data sources include fossils, anatomy, molecules, and DNA analysis
• Trees are updated as new species and data are discovered
• Phylogenies identify useful traits
• Phylogenies are important in medicine, agriculture, and taxonomy
• Cladistics groups organisms into clades (monophyletic groups) based on common ancestry
• A clade includes all organisms from a common ancestor and all its descendants
• Example: Amniota clade (organisms with amniotic eggs)
• A shared ancestral trait is present in all descendants; vertebrate backbone
• A shared derived trait evolved more recently and is not found in all ancestors; amniotic egg
• Sorting homologous vs. analogous traits is complex
• DNA technology provides huge amounts of data to analyze
• Trees are often revised using the principle of maximum parsimony (simplest evolutionary path is preferred)
• Some propose "web of life" or "ring of life" diagrams to reflect complex evolutionary relationships

Natural Selection

• Natural selection involves traits that improve survival and reproduction become more common
• Long-necked tortoises in the Galápagos could reach more food, survived droughts, and passed on the trait
• Darwin's 3 Principles: (1) Traits are inherited from parents to offspring, (2) More offspring than resources lead to competition, (3) Variation in offspring offers survival advantages
• Adaptation: Inherited traits increasing fitness in a specific environment
• Modern Synthesis: Darwin’s theory integrated with Mendelian genetics (1940s), links natural selection with genetic variation and population change (microevolution to macroevolution)
• Stabilizing Selection: Favors average traits
• Directional Selection: Favors one extreme
• Diversifying Selection: Favors both extremes over the average
• Sexual Selection: Traits increase mating success leading to sexual dimorphism
• Frequency-Dependent Selection: Advantage depends on frequency of traits
• Negative frequency-dependent selection means rare traits are favored, maintaining diversity
• Positive frequency-dependent selection means common traits are favored and reduces diversity
• Genetic Drift: Random changes in allele frequency
• Bottleneck Effect: Disaster reduces population and genetic diversity
• Founder Effect: Small group starts new population with a limited gene pool
• Gene Flow: Movement of genes between populations via migration or pollination
• Mutation: Source of new genetic variation that can be harmful, neutral, or beneficial
• Non-Random Mating: Mating preference alters gene frequencies
• Environmental Variance: Environment affects traits, such as temperature-dependent sex determination in reptiles

Systematics and Taxonomy

• Systematics classifies organisms and studies their evolutionary relationships
• It names the diversity of life
• It understands evolutionary relationships using the phylogenetic tree
• The old system had 5 kingdoms (animals, plants, fungi, protists, bacteria), based on morphology
• The modern system is based on genetic, biochemical, and molecular evidence
• Carl Woese introduced the three-domain system: Bacteria, Archaea, Eukarya
• Taxonomy is the branch of systematics focused on naming, defining, and classifying organisms using a hierarchical classification system
• The hierarchical classification system goes from broad to specific (Domain to Species)
• Carl Linnaeus introduced it and is known as the “Father of Taxonomy.”
• Binomial Nomenclature: Scientific naming system using Genus and Species
• Genus is capitalized, species is lowercase, both are italicized
• A ninth category, subspecies, is sometimes used
• How Species Are Named: (1) Specimens are grouped, (2) Existing names are checked, (3) If new, a detailed description and new name are created, (4) Name and description must be formally published

Viruses

• Viruses are non-cellular parasitic entities that infect all forms of life
• They rely completely on host cells to replicate and assemble new virions
• No fossil record exists, and origins are unclear
• Virions are tiny (20–250 nm), visible only under an electron microscope
• Virions consist of a nucleic acid core (DNA or RNA), protein capsid, and sometimes a lipid envelope
• Capsids come in 4 main shapes: helical, icosahedral, enveloped, head-and-tail
• Viral genomes vary: DNA or RNA; single or double-stranded; linear, circular, segmented
• DNA viruses rely on host enzymes
• RNA viruses must encode their own enzymes and mutate faster
• Retroviruses reverse-transcribe RNA to DNA
• Past classification systems used genome type, capsid shape, and envelope
• The Baltimore classification groups viruses by how they produce mRNA
• Plant Viruses enter via damage and spread through plasmodesmata or are inherited
• Common symptoms: hyperplasia, hypoplasia, necrosis, malformed tissues, discoloration
• Animal Viruses often enter via membrane fusion or endocytosis
• Acute infections are short-term, chronic infections are long-term, latent infections are dormant but can reactivate, and asymptomatic infections show no visible symptoms

Prokaryotes, Protists, and Fungi

• Prokaryotic cells have no nucleus or membrane-bound organelles
• Prokaryotes come in shapes of spheres (cocci), rods (bacilli), and spirals (spirilla)
• Prokaryotes reproduce asexually via binary fission, but can exchange DNA (horizontal gene transfer)
• Prokaryotes are found in nearly every environment on Earth
• Prokaryotes have roles in nutrient cycling and are decomposers, and have symbiotic relationships
• Extremophiles (Archaea) live in extreme conditions: heat, salt, acidity
• Protists are eukaryotic organisms (have a nucleus) but and are not plants, animals, or fungi
• Autotrophic protists perform photosynthesis, heterotrophic protists eat other organisms, and mixotrophic protists do both
• Protists are the base of aquatic food chains and some cause diseases
• Fungi are eukaryotic and mostly multicellular (except yeasts)
• Fungi are heterotrophs that absorb nutrients from surroundings
• Fungi cell walls are made of chitin
• Fungi are decomposers that break down organic matter
• Mutualistic fungi form mycorrhizae with plant roots and lichens with algae/cyanobacteria

Plant Diversity

• Plants evolved from green algae and adapted to land with a waxy cuticle, stomata, and vascular tissues
• Nonvascular Plants (Bryophytes) include mosses, liverworts, and hornworts
• Nonvascular Plants have no true roots, stems, or leaves
• Nonvascular Plants are gametophyte dominant (haploid) and rely on water for fertilization
• Seedless Vascular Plants include ferns, club mosses, horsetails
• Seedless Vascular Plants have true vascular tissue (xylem, phloem)
• Seedless Vascular Plants are sporophyte dominant (diploid) but still rely on water for fertilization
• Seed Plants have a dominant sporophyte generation
• Seed Plants use pollen (male gametophyte) for fertilization and do not need water
• Seed Plants produce seeds (embryo + food supply + protective coat)
• Gymnosperms (“naked seeds”) include conifers, cycads, ginkgo and have seeds exposed (not in fruit)
• Angiosperms (“flowering plants”) are the most diverse group and have seeds enclosed in fruit (develops from ovary)
• Angiosperms use flowers to attract pollinators and undergo double fertilization (zygote + endosperm)
• Life cycles show a shift from gametophyte-dominant (nonvascular) to sporophyte-dominant (vascular and seed plants) and increasing independence from water for reproduction

Animal Phyla

• Animal phyla vary in body symmetry, tissue layers, and key features
• Porifera (Sponges) are asymmetrical with no true tissues, filter feeders, and have pores and spicules for support
• Cnidaria (Jellyfish, Corals, Hydra) have radial symmetry, diploblastic tissues, stinging cells (cnidocytes), and a gastrovascular cavity
• Platyhelminthes (Planarians, Tapeworms) have bilateral symmetry, triploblastic tissues, flat bodies, are aceolomate, and some are parasitic
• Nematoda (Roundworms, Hookworms) have bilateral symmetry, triploblastic tissues, are pseudocoelomate, and have a complete digestive tract
• Annelida (Earthworms, Leeches) have bilateral symmetry, triploblastic tissues, segmented bodies, are coelomate, and have a closed circulatory system
• Mollusca (Snails, Clams, Squids) have bilateral symmetry, triploblastic tissues, soft bodies with shells, muscular foot, and a mantle
• Arthropoda (Insects, Spiders, Crabs) have bilateral symmetry, triploblastic tissues, an exoskeleton (chitin), jointed appendages, and segmentation
• Echinodermata (Sea Stars, Sea Urchins) have radial symmetry as adults and bilateral as larvae, are triploblastic, and have a water vascular system, tube feet, and an endoskeleton
• Chordata (Fish, Amphibians, Birds, Mammals) have bilateral symmetry, triploblastic tissues, a notochord, dorsal nerve cord, post-anal tail, and pharyngeal slits

Speciation

• A species is a group of organisms that can interbreed and produce viable, fertile offspring
• They share similar DNA, traits, and behaviors due to shared genetic information
• Phenotype can be misleading
• Speciation is the formation of new species from a common ancestor and drives biodiversity
• It requires genetic divergence and reproductive isolation
• Allopatric Speciation ("different homeland") happens when populations are geographically separated
• No gene flow occurs as populations evolve independently because of dispersal and vicariance
• Adaptive Radiation is when a single species spreads out and adapts to different ecological niches
• Sympatric Speciation ("same homeland") occurs without geographic separation, often results from genetic mutations during cell division (polyploidy)
• Reproductive Isolation prevents gene flow between diverging populations
• Prezygotic Barriers (before fertilization) include temporal isolation (different breeding seasons) and habitat isolation (different environmental preferences)
• Postzygotic Barriers (after fertilization): Zygote forms but the embryo fails to develop or the offspring is sterile