Biology Reproduction and Energy Systems

Reproduction

• Reproduction occurs sexually (two parents) or asexually (one parent).
• Offspring are the result of reproduction.
• Mitosis is asexual reproduction, splitting a parent cell into identical daughter cells.
• Meiosis produces gametes (sex cells): oocytes (female) and spermatocytes (male).
• Meiosis halves the genetic information.
• Fertilization combines sex cells to form a zygote.
• A zygote develops into an embryo via mitosis, then an organism.
• Sexual reproduction increases species survival chance.
• Somatic cells undergo mitosis; specialized cells undergo meiosis.
• Most complex organisms (mammals, plants) use sexual reproduction.
• Some plants can reproduce asexually (budding, spore formation, fission).
• Simple organisms (algae, bacteria) often use asexual reproduction due to speed.

Energy for Living Systems

• Living organisms need constant energy and matter.
• Solar energy (photons) is the ultimate source.
• Plants (autotrophs) convert sunlight to usable energy (photosynthesis).
• Heterotrophs obtain energy through consuming plants or other animals.
• Organisms die, their matter is recycled; energy and matter are recycled.
• Living organisms capture and store energy to fuel processes (metabolism, reproduction, etc.).
• Too much or too little energy leads to negative outcomes (weight gain, death).
• Changes in producers impact entire ecosystems (energy flow).

Homeostasis and Cell Membranes

• Homeostasis is maintaining stable internal conditions.
• Cell membranes regulate molecular transport in and out of cells.
• Passive transport: molecules move without energy input (diffusion, facilitated diffusion).
• Molecules spread out evenly (diffusion).
• Facilitated diffusion: molecules use transport proteins to pass through.
• Active transport: cells actively move molecules, requiring energy.
• Important for cell function (metabolism, waste disposal, protein synthesis).

Feedback Mechanisms

• Feedback mechanisms regulate processes to maintain homeostasis.
• Negative feedback maintains a stable level (e.g., body temperature).
• Positive feedback amplifies a process away from a level (e.g., fruit ripening).
• Errors in feedback mechanisms can disrupt processes (e.g., diabetes).

Energy Conversion: Photosynthesis and Cellular Respiration

• Living organisms need energy to survive and reproduce.
• The sun's energy must be converted into usable forms.
• Plants use photosynthesis to produce sugar and oxygen.
• Photosynthesis is endergonic, requiring energy input (light).
• Cells use sugar to make ATP (adenosine triphosphate), the usable cellular energy form.
• Cellular respiration breaks down sugar, releasing energy.
• Cellular respiration is exergonic, releasing energy.
• Products of cellular respiration are carbon dioxide and water; these are used in photosynthesis.

Cellular Respiration: Aerobic and Anaerobic

• Most eukaryotic cells need oxygen for cellular respiration.
• Cellular respiration breaks down molecules, producing ATP.
• Aerobic respiration: requires oxygen; yields 36 net ATP per glucose molecule.
• Stages: glycolysis, transition reaction, Krebs cycle, and oxidative phosphorylation.
• Anaerobic respiration: occurs without oxygen; produces less ATP.
• Fermentation: an anaerobic process after glycolysis; produces little ATP.

Photosynthesis

• Photosynthesis converts sunlight into food in plants and some other organisms.
• Photosynthesis is the reverse of cellular respiration.
• Chlorophyll, a pigment, absorbs blue and red light, reflecting green.
• Chlorophyll is located in thylakoid membranes of chloroplasts; responsible for the green color of plants.
• Sunlight energizes electrons in chlorophyll, initiating the process.

Taxonomy

• Taxonomic classification: hierarchical system grouping organisms from broad to specific, finishing with binomial nomenclature (genus and species).
• Binomial nomenclature for identification of organisms.
• Carolus Linnaeus pioneered it.
• Categories (taxa): Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
• Domains (accommodating new data): Archaea, Bacteria, Eukarya.

Archaea

• Archaea are prokaryotes, different from bacteria in ribosomal RNA.
• Thrive in extreme environments (high temperature, acidity, salinity).
• Have different cell wall and plasma membrane structures.
• DNA is circular.
• Reproduce via binary fission.
• Diverse energy sources: sunlight, inorganic materials, organic materials.
• Include thermophiles, acidophiles, and hypersaline organisms.

Protists

• Protists are eukaryotes that don't fit easily in other kingdoms; unicellular and mostly aquatic with various nutrition methods.
• Animal-like protists (protozoa) ingest food.
• Plant-like protists (protophyta) make food through photosynthesis.
• Fungus-like protists absorb nutrients. Examples include diatoms, dinoflagellates, and euglenas.

Fungi and Plants

• Fungi are heterotrophic; obtain nutrients by decomposing organic matter.
• Plant cell walls are made of cellulose; they produce food through photosynthesis.
• Fungi and plants are both eukaryotic.
• Fungi have cell walls made of chitin; Plants have cell walls made of cellulose.
• Both evolved from aquatic protists.
• Fungi and plants evolved from different branches, with complimentary features, like vascular tissue or spore dispersal mechanisms.

Origin of Life

• Life on Earth started ~4.5 billion years ago with unicellular organisms.
• Early Earth very different (no atmosphere, hot), with meteorites delivering water and organic molecules (like compounds that form amino acids).
• Lightning provided energy for creating simple organic compounds from inorganic materials.
• Organic compounds formed complex molecules, eventually enclosed in structures (coacervates and protobionts).
• Miller-Urey experiment confirmed Oparin's (organic molecules' development leading to life) theory through experimental evidence.

Animals

• Animals are multicellular eukaryotes (Kingdom Animalia).
• Eight characteristics defining animals: eukaryotic, multicellular, heterotrophic, free-moving, symmetry, body cavity, tissues, presence/absence of vertebral column.
• Reproduction can be sexual or asexual.