Cell Organelles & Prokaryotic vs. Eukaryotic Cells

• Review of the diversity of living things

Cell Organelles & Prokaryotic vs. Eukaryotic Cells

• Prokaryotic cells are simple, lack a nucleus, and have no membrane-bound organelles
• Bacteria are an example of prokaryotic cells
• Eukaryotic cells are complex, have a nucleus, and contain membrane-bound organelles
• Plants, animals, fungi, and protists are examples of eukaryotic cells
• Organelles are key components of cells
• The nucleus stores DNA and controls cell functions
• Mitochondria are the powerhouse of the cell, producing ATP (energy)
• Ribosomes synthesize proteins
• The endoplasmic reticulum (ER) has two forms: smooth ER, which synthesizes lipids, and rough ER, which synthesizes proteins
• The Golgi apparatus packages and ships proteins
• Lysosomes digest waste in animal cells
• Chloroplasts conduct photosynthesis in plants
• The cell wall provides structure and support to plants, fungi, and bacteria
• Vacuoles store water and nutrients, and are large in plant cells

Taxonomy

• Classification categorizes organisms from broad to specific groups: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
• Domains are bacteria, archaea, and eukarya
• Kingdoms include bacteria, archaea, plants, fungi, and animals
• Taxons are the smaller groups within this classification system
• Genus names are capitalized, species names are lowercase
• Scientific names are italicized such as Homo sapiens

Three Species Concepts

• The biological species concept defines species as organisms that can interbreed and produce fertile offspring
• The morphological species concept classifies species based on their physical traits
• The phylogenetic species concept defines species based on common ancestors and evolutionary relationships, often represented by a web or tree

Evolutionary Relatedness & Evidence (1.2)

• Anatomical evidence includes appearance and morphology
• Using fossils to determine relatedness indicates changes over time
• Homologous structures have the same structure but different functions
• Bones of a human arm, horse leg, bat wing, and whale flipper have similar bone structures but different functions
• Embryonic development suggests common ancestry, as early developmental stages are similar across vertebrates, which go through stages where they have gills like fish
• Physiological evidence looks at the functioning of organisms
• This includes biochemistry, proteins, and DNA
• Similar DNA and proteins indicates a close relationship
• Comparing DNA indicates that fungi are closer related to animals than plants
• Analogous structures have different structures but the same function

Types of Diversity (1.4) & Importance

• Genetic diversity refers to variation within species
• Ensures survival by allowing adaptation to environmental changes and resistance to diseases, and prevents inbreeding problems
• Species diversity refers to the number of species inhabiting an ecosystem
• Enhances ecosystem stability; is important for pollination and decomposition; provides food and habitat
• Ecosystem diversity refers to different habitats and communities
• Ensures resilience against climate change, natural disasters, and human impact; supports various life forms
• Importance: Supports ecosystems, food webs, medicine, adaptation to environmental changes
• Food security, medicine development, ecosystem services, and overall environmental balance

Viruses

• General characteristics: Non-living, require a host to reproduce as they lack cellular structure like cytoplasm and other organelles, and can cause plant diseases
• Viruses are composed of DNA or RNA plus a protein coat
• Viruses are classified based on their shape or capsid
• Replication cycles:
• Lytic Cycle: Takes place in host cell cytoplasm, uses host cell machinery to copy viral DNA/RNA, resulting in immediate host takeover
• The host cell is destroyed and new viruses are released
• Lysogenic Cycle: The virus places its viral DNA into host cell's nucleus where it becomes part of the hosts chromosomes, and may become active later
• Herd immunity helps more vulnerable individuals
• Vaccination limits spread
• Fewer immune people cause wider disease spread
• Methods to fight viruses:
• No antibiotics are effective
• Vaccines prevent viral infections
• Antiviral drugs limit viral replication
• Rely on natural immune response (wait)

Endosymbiosis (2.3)

• Eukaryotic cells evolved when one prokaryotic cell engulfed another
• Over time, the engulfed cells became organelles
• Evidence for endosymbiosis:
• Mitochondria & chloroplasts have their own DNA (circular like bacteria)
• Contain double membranes
• They reproduce independently via a process similar to binary fission
• Ribosomes are more similar to prokaryotic ribosomes than eukaryotic ones

Dichotomous Key

• A tool used to determine the identity of an object/organism by narrowing down identity
• Can determine specific species

Aquatic to Land Adaptations (3.1)

• For aquatic algae to survive on land and evolve into plants, the plants needed to:
• Prevent drying out to prevent water loss: cuticle, stomata
• Reproduction: Seeds, pollen
• Early land plants were small and grew in damp areas, still depending on osmosis and diffusion to transport water and nutrients
• The shoot system creates a support system to lift plants toward sunlight
• The root system develops to help plants move water and nutrients from the environment into their cells

Algae as Fuel

• Fast-growing algae absorbs CO2 and produces biofuel
• It is a renewable resource because, unlike fossil fuels, algae can be grown continuously
• Carbon-neutral: Algae absorbs CO2 during growth to reduce greenhouse gas emissions
• High energy yield: Algae produces more biofuel per acre than traditional crops
• Does not compete with food crops: Algae does not take up farm land needed for food production
• Can be grown in various environments (saltwater, wastewater, or non-arable land) to make it more versatile as a fuel source
• Is less harmful to the environment: Algae-based biofuels generates less water compared to traditional fossil fuel extraction and refining

Kingdoms Overview

• 6 Kingdoms: Bacteria, Archaea, Protista, Fungi, Plantae, Animalia
• Classified by shape (cocci, bacilli, spirilla), metabolism (aerobic or anaerobic), cell composition
• Bacteria are single-celled, prokaryotic organisms that can be autotrophic or heterotrophic
• Reproduce by binary fission or conjugation
• Bacteria are decomposers and aid digestion and some cause diseases
• Gram stain shows cell-wall composition
• Gram-positive bacteria have a thick protein layer (purple)
• Gram-negative bacteria have a thin protein layer (pink)
• Archaea classification is based on habitat and metabolism
• Methanogens produce methane
• Halophiles thrive in salty environments
• Thermophiles thrive in extreme heat
• Psychrophiles survive in cold
• Archaea are single-celled prokaryotic organisms that are genetically distinct from bacteria
• Cell walls lack the peptidoglycan found in bacterial cell walls
• They have special enzymes, and play roles in nutrient cycling
• Extremophiles adapted to extreme conditions such as heat, cold, salt, and acid
• Psychrophiles thrive in freezing temperatures
• Anaerobic metabolism: can survive without oxygen
• Thick cell walls & membranes: contain ether-linked lipids
• Radiation and drought resistance: able to endure high UV radiation and drought
• Protista are a miscellaneous group of eukaryotic organisms
• Fungi are eukaryotic decomposers
• Plantae are photosynthetic, have cell walls and are eukaryotic organisms
• Animalia have no cell walls, consume food and include eukaryotic organisms

Climate Change & Biodiversity (3.5)

• Climate change causes: habitat loss, ocean acidification, and temperature shifts
• Habitat loss leads to species extinction
• Ocean acidification affects marine life
• Temperature shifts disrupt migration and reproduction
• Climate change impacts ecosystem balance, resources, and human health and economy

Climate Change & Reproduction (Key Points)

• Incubation temperature determines gender among reptiles
• In some reptiles, the egg's temperature decides if they become male or female
• Cooler temperatures contribute to more females being born
• Warmer temperatures contribute to more males being born
• Climate change is impacting global temperatures
• Creates an imbalance between males and females
• Tuatara Case Study (New Zealand Reptile): warmer temperatures result in mostly male populations
• Too many males means not enough females to reproduce, which could lead to population decline
• Population decline is a problem because, if a species has too few females left to lay eggs, a species population may disappear

Climate Change & Ecosystem Vulnerability

• Ecosystems are vulnerable because:
• Many species rely stable temperatures
• Temperature changes impact food sources, migration patterns, and habitat stability
• Extreme weather disrupt entire ecosystems
• Ocean acidification impacts marine life and coral reefs

Observed Effects on Ecosystems

• Rising temperatures result in more male reptiles and fewer females
• Polar ice melting results in loss of habitat for Arctic species
• Shifting seasons result in birds and insects migrating at the wrong times, affecting pollination
• Warmer oceans cause coral bleaching, disrupting marine biodiversity

Projected Impacts If Climate Change Isn't Slowed

• Species extinction occurs due to reproductive failures, resulting in too many males or not enough females
• Loss of biodiversity can weaken ecosystems
• Food chain disruptions affect predators and prey
• Increased natural disasters damage habitats and human communities

Ways to Help Biodiversity Adapt & Reduce Damage

• Protect and restore habitats
• Reduce greenhouse gas emissions
• Use artificial shading/cooling in nesting sites to help balance reptile gender
• Promote sustainable farming and fishing
• Support wildlife corridors to help species migrate to suitable climates