Fungi Structure and Reproduction

Chapter 31 – Fungi

• Fungi are eukaryotic and heterotrophic, absorbing nutrients externally
• Fungi cell walls are made of chitin
• Septate hyphae are divided by walls
• Coenocytic hyphae have continuous cytoplasm
• Mycelium is a tangled mass of hyphae and its large surface area allows for great absorption
• Asexual reproduction via mitosis produces spores for new fungi
• Sexual reproduction includes plasmogamy, heterokaryotic stage, karyogamy, and meiosis
• Plasmogamy involves the fusion of cytoplasm from two parent hyphae
• The heterokaryotic stage is when nuclei from fused hyphae do not fuse immediately
• The nuclei fuse from the heterokaryotic stage during karyogamy to form a zygote (2n)
• Meiosis follows karyogamy to produce spores
• Fungi decompose organic material, recycling nutrients
• Lichens are mutualistic relationships between fungi and photosynthetic partners
• Mycorrhizae are mutualistic relationships between fungi and plant roots
• Some fungi are parasites and can infect plants and animals

Chapter 35 – Vascular Plant Structure, Growth, and Development

• Plant organs include roots, stems, and leaves
• Roots anchor plants, absorb water and minerals, and store food
• Stems support plants and transport substances
• Leaves are the primary site of photosynthesis
• Dermal tissue is the outer layer, including the epidermis and waxy cuticle
• Xylem transports water and minerals upwards from the roots
• Phloem transports sugars down or around the plant
• Ground tissue includes parenchyma for photosynthesis, collenchyma for support, and sclerenchyma for structure
• Plants exhibit indeterminate growth from meristems
• Apical meristems facilitate primary growth in length
• Lateral meristems facilitate secondary growth in width
• The vascular cambium adds xylem and phloem
• The cork cambium produces bark (periderm)

Chapter 36 – Resource Acquisition and Transport in Vascular Plants

• Water moves from high water potential (Ψ) to low Ψ in short-distance transport
• Water potential is affected by solute concentration and pressure
• Water enters roots through osmosis in short distance transport
• In long-distance transport Xylem transports water from roots to leaves
• Transpiration is Water evaporation from stomata pulling water upward
• Cohesion involves water molecules sticking to each other
• Adhesion involves water molecules sticking to xylem walls
• Phloem transports sugars from source to sink in long distance transport
• Pressure from sugar loading pushes sap to needed areas

Chapter 37 – Soil and Plant Nutrition

• The A horizon (topsoil) is rich in organic matter and optimal for root growth
• Macronutrients such as N, P, and K are needed in large quantities
• Micronutrients such as Fe and Zn are needed in small amounts
• Rhizobium bacteria fix nitrogen in root nodules
• Nitrogen fixation involves converting N₂ to NH₄⁺
• Nitrifying bacteria convert NH₄⁺ to NO₃⁻ (usable form)
• Denitrifying bacteria convert NO₃⁻ back to N₂
• Rhizobium bacteria form mutualistic relationships with legumes
• Mycorrhizae enhance mineral and water absorption

Chapter 38 – Angiosperm Reproduction and Biotechnology

• Angiosperms have a life cycle with alternation of generations
• The sporophyte (2n) is the dominant generation
• The gametophyte (n) is microscopic
• The stamen (male) includes the anther, which makes pollen
• The carpel (female) includes the ovary, which makes ovules that become seeds
• Pollination is Pollen transfer to the stigma
• Double fertilization involves one sperm fertilizing the egg to form a zygote (2n)
• A second sperm fertilizes the central cell to form endosperm (3n)
• Seed consists of embryo + endosperm + seed coat
• Fruit is a mature ovary that aids in dispersal of seeds
• GMOs are genetically modified organisms with altered traits like pest resistance
• GMOs are controversial for health, environmental, and ethical reasons

Chapter 39 – Plant Hormones and Responses

• Auxin promotes cell elongation and phototropism
• Cytokinins stimulate cell division and delay aging
• Gibberellins promote seed germination and stem elongation
• Abscisic acid (ABA) slows growth, closes stomata during drought, and induces dormancy
• Ethylene promotes fruit ripening and leaf drop
• Blue light receptors control phototropism
• Phytochromes control germination, flowering, and shade response
• Circadian rhythms are 24-hour internal clocks
• Photoperiodism is flowering based on day/night length
• Short-day plants flower when nights are long
• Long-day plants flower when nights are short
• Phytochrome ratio (red/far-red light) controls photoperiodism

Chapter 21 – Genomes and Their Evolution

• Genome size does not correlate with gene number
• Prokaryotes have higher gene density compared to complex vertebrates
• Alternative RNA splicing generates multiple proteins from one gene
• Noncoding DNA does not code for proteins
• Transposons and retrotransposons can move within the genome
• Polyploidy is genome duplication common in plants
• Chromosome fusion occurred in human evolution (chromosome 2)
• Conserved genes suggest close evolutionary relationships

Chapter 22 – Descent with Modification (Darwin)

• More offspring are born than can survive
• Individuals vary, and traits can be inherited
• Favorable traits increase survival and reproduction rates
• Direct observation shows evolution by antibiotic and pesticide resistance
• Homology indicates similar structure, different function, due to a common ancestor
• Fossil records show transitional forms
• Biogeography shows island species resemble mainland relatives
• Convergent evolution leads to similar traits in unrelated organisms due to similar environments
• Homologous structures share a common ancestor
• Analogous structures have the same function but different ancestors

Chapter 23 – Evolution of Populations

• Evolution is defined by change in allele frequencies
• Genetic variation arises from mutations, gene duplication, and sexual reproduction
• Natural selection is the only adaptive mechanism
• Genetic drift is random and impacts small populations more
• The bottleneck effect results from drastic population reduction
• The founder effect is when a few individuals start a new population
• Gene flow is the movement of genes between populations
• Sexual Selection increases mating sucess

Chapter 24 – The Origin of Species

• Species are groups that interbreed and produce fertile offspring
• Prezygotic barriers prevent fertilization, including habitat, behavior, and mechanical isolation
• Postzygotic barriers result in hybrid death or sterility
• Allopatric speciation occurs with geographic barriers
• Sympatric speciation occurs without physical barriers, such as polyploidy
• Hybrid zones are where species overlap and interbreed
• Reinforcement strengthens reproductive barriers
• Fusion merges species
• Stability allows hybrids to persist

Chapter 25 – History of Life on Earth

• Earth is 4.6 billion years old
• First life was prokaryotes, 3.5 billion years ago
• The oxygen revolution was from photosynthetic bacteria
• Eukaryotes evolved via endosymbiosis
• Fossil records indicate the order of evolution
• Transitional fossils show gradual changes
• Key events include prokaryotes, oxygen, eukaryotes, multicellular life, Cambrian explosion, and land colonization
• Mass extinctions include the Permian and Cretaceous events
• Adaptive radiation is rapid speciation after extinctions

Chapter 26 – Phylogeny and the Tree of Life

• The Linnaean system classifies organisms into kingdom, phylum, class, order, family, genus, species
• Phylogenetic trees show evolutionary relationships
• Nodes represent common ancestors
• Branches represent lineages
• A monophyletic group includes an ancestor and all its descendants
• Shared derived characters build phylogenetic trees
• Homologies build phylogenies
• Convergent evolution can mislead by creating analogous traits

Chapter 27 – Bacteria and Archaea

• Prokaryotes are unicellular, lack a nucleus, and have DNA in a nucleoid
• Prokaryote shapes include cocci (spheres), bacilli (rods), and spirilla (spirals)
• Gram+ bacteria have thick peptidoglycan walls and stain purple
• Gram– bacteria have thin walls, an outer membrane and stain pink being more resistant to antibiotics
• Binary Fission is how bacteria reproduce asexually
• Genetic variation occurs through transformation, transduction, and conjugation
• Transformation is when bacterium uptake DNA from the environment
• Transduction involves virus transferring DNA
• Conjugation is direct transfer using a pilus
• Roles in ecosystems include decomposers and nitrogen fixers
• The human gut microbiome aids digestion and immunity
• Legumes + Rhizobium fix nitrogen in root nodules

Chapter 52 – Ecology and the Biosphere

• Climate patterns are caused by sunlight, Earth’s tilt, and air circulation cells
• Tropics have direct sunlight, leading to warm and wet conditions
• Deserts are at 30° N/S with dry descending air
• Mountains create rain shadows
• Oceans moderate temperature
• Climate change is caused by rising CO₂ from fossil fuels
• Climate change leads to warming, sea-level rise, and disrupted weather patterns
• Tropical forests have high rainfall and biodiversity
• Deserts are dry with hot days and cold nights
• Savannas have grass and few trees and are fire-adapted
• Chaparral is shrubland with dry summers
• Temperate grasslands are prairies adapted to fire and grazing

Chapter 53 – Population Ecology

• Type I survivorship curves show high survival (humans)
• Type II survivorship curves show constant death rate (squirrels)
• Type III survivorship curves show high infant mortality (fish, plants)
• Exponential growth is a J-shaped curve without limits
• Logistic growth is an S-shaped curve with carrying capacity (K)
• Life history traits involve trade-offs between survival and reproduction
• Density-dependent regulation includes competition, disease, and predation

Chapter 54 – Community Ecology

• Competition harms both species
• Predation benefits one species and harms another
• Herbivory is when an animal eats a plant
• Mutualism benefits both species
• Parasitism benefits one species and harms another
• Commensalism benefits one species, with no effect on the other
• The competitive exclusion principle means two species competing for the same niche results in one species extinction
• An ecological niche is an organism’s role + resources
• Trophic structure is food chain levels
• Keystone species have huge impacts, not always abundant
• Ecosystem engineers change the environment

Chapter 55 – Ecosystems and Restoration Ecology

• GPP is total energy from photosynthesis
• NPP is GPP – energy used by plants
• Only ~10% of energy moves to the next trophic level
• Evaporation → condensation → precipitation: Water cycle
• Photosynthesis + respiration and burning fossil fuels adds CO₂: Carbon cycle
• Fixation, nitrification, uptake, denitrification: Nitrogen Cycle
• Weathering rocks → soil → plants → animals: Phosphorus cycle