Overview
This lecture provides a comprehensive review of key Biology topics commonly found in the ENEM exam, focusing on core concepts like levels of biological organization, ecology, evolution, classification, cell biology, genetics, and scientific method.
Levels of Biological Organization
- Biological organization starts from atoms, molecules, cells, tissues, organs, systems, to organisms.
- The cell is the basic unit of life; unicellular and multicellular organisms exist.
- Organs form systems, and systems together form an organism.
- Populations are groups of the same species in the same place and time.
- Communities consist of different species living together.
- Ecosystem = community + non-living environment.
- Biosphere includes all ecosystems on Earth.
Ecology & Environmental Impacts
- Producers (e.g., plants) convert solar energy into chemical energy through photosynthesis.
- Food chains and webs illustrate energy transfer among producers, consumers, and decomposers.
- Trophic levels: producers (1st), primary consumers (2nd), secondary (3rd), etc.
- Environmental impacts include habitat loss, introduction of exotic species, climate change, and pollution.
- Edge effect and habitat fragmentation harm biodiversity; ecological corridors help preserve species.
- Primary succession: colonization of lifeless areas; secondary succession: recovery after disturbance.
Ecological Relationships
- Intraspecific (within species) and interspecific (between species) interactions can be harmonious or disharmonious.
- Examples: mutualism (both benefit), parasitism (one benefits, one harmed), commensalism (one benefits, other unaffected), competition, predation, amensalism, cannibalism, colony, society.
Evolution & Classification
- Evolution is a fact; natural selection favors the best-adapted individuals for their environment.
- Species: group capable of interbreeding and producing fertile offspring.
- Speciation occurs via reproductive isolation—geographic, temporal, behavioral, or mechanical barriers.
- Classification: domains (Bacteria, Archaea, Eukarya) and five kingdoms (Monera, Protista, Fungi, Plantae, Animalia).
- Binomial nomenclature uses Genus (capitalized) and species (lowercase, italics/underlined).
Cell Biology & Genetics
- Cell theory: all living beings consist of at least one cell; viruses are not considered alive by this definition.
- Prokaryotic cells (Bacteria, Archaea) lack membrane-bound organelles; eukaryotic cells (plants, animals, fungi, protists) have them.
- Key organelles: mitochondria (energy), nucleus (genetic info), ribosomes (protein synthesis), lysosomes (cell digestion), endoplasmic reticulum, Golgi complex.
- Plant cells have chloroplasts, cell wall, large vacuoles; animal cells do not.
- Plasma membrane function: selective permeability, passive (diffusion, osmosis) and active transport.
- Gene: DNA segment coding for a trait; chromosomes are condensed DNA.
Genetics & Immunology
- ABO blood system: A, B (codominant), O (recessive); RH factor (+/-).
- Universal donor: O-, universal recipient: AB+.
- Vaccines induce active immunity (antigen stimulates own antibodies); serum provides passive, temporary immunity (direct antibodies).
- Vaccine prevents disease by enabling quick immune response before symptoms.
Scientific Method
- Steps: observation, question, hypothesis, experimentation, results, conclusion.
- Hypotheses must be testable; experiments must be repeatable.
- Control groups (e.g., placebo) are essential in scientific trials.
Key Terms & Definitions
- Ecological succession — Sequential change in species composition in an ecosystem over time.
- Edge effect — Negative impact at boundaries between habitats.
- Speciation — Process by which new species arise.
- Symbiosis — Close ecological relationship between different species.
- Abiogenesis — Theory that life arises from non-living matter.
- Passive transport — Movement of substances across membranes without energy expenditure.
Action Items / Next Steps
- Review biogeochemical cycles, especially the nitrogen cycle.
- Study differences between cell types and organelle functions.
- Practice scientific method steps with sample experiments.
- Rest the day before ENEM; avoid heavy study or stress.
- Check ENEM questions for Ecology, Genetics (blood types, vaccines), and Scientific Method.
- Follow teacher social media for post-exam discussions and further resources.