Key Concepts in Biology: Variables, Energy, Genetics, and More
Key Concepts in Biology
In experiments, the independent variable is manipulated, while the dependent variable responds. The independent variable is plotted on the x-axis, and the dependent variable on the y-axis.
Energy and Ecosystems
Lions hunt in groups to conserve energy. The 10% rule states that approximately 10% of energy is transferred between trophic levels in food chains. Net energy gain refers to the final amount of energy gained or lost.
Cellular Biology
Prokaryotic cells are single-celled organisms like bacteria, while eukaryotic cells are found in multicellular organisms like plants and animals.
Genetics and Heredity
Parentage can be determined by comparing DNA for similar genes. Humans have 23 chromosome pairs, inheriting 23 from each parent. An allele is a version of a gene. A karyotype is a graph showing chromosome pairs. Each genotype consists of two alleles, represented by different letters. A genetic match requires 50% of alleles from each parent.
Breaking bonds releases energy. Carbohydrates, lipids, and proteins contain carbon, hydrogen, and oxygen. Proteins also contain nitrogen. Organisms consume macromolecules like carbohydrates from plants, break their bonds to release energy, and then reassemble new macromolecules. Enzymes, which are proteins, speed up reactions by breaking and creating bonds. pH and temperature affect enzyme activity.
Nutrient Cycles
Nitrogen enters the atmosphere through denitrification by bacteria and is removed by nitrogen-fixing bacteria in the soil. These bacteria make nitrogen usable for plants. Plants absorb nitrogen through their roots. Herbivores consume plants containing nitrogen, and when they die or expel waste, nitrogen returns to the soil. Two types of nucleic acids are RNA and DNA.
Evolution and Adaptation
Organisms with advantageous adaptations, such as speed, strength, or coat color, have a better chance of obtaining limited resources. This leads to survival of the fittest and more organisms with favorable traits. Tusklessness in elephants is a mutation that has become beneficial due to poaching, a selective pressure that has increased the survival and reproduction of tuskless elephants.
DNA Fingerprinting
DNA fingerprinting (Gel Electrophoresis) is used to identify individuals by analyzing unique DNA fragments. This technique was used to identify elephant poachers by matching DNA from tusks to suspects. Since every individual’s DNA is unique, DNA fingerprinting can be used to determine identity.
Cell Division
Mitosis is the process by which a cell replicates its chromosomes and segregates them, producing two identical nuclei for cell division. Mitosis is followed by the division of the cell’s contents into two daughter cells with identical genomes. Mitosis is essential for growth and healing. Mitosis is divided into five phases: prophase, metaphase, anaphase, and telophase. Interphase is the resting phase. During prophase, visible chromosome pairs appear. In metaphase, chromosomes align in the middle. In anaphase, cells pull apart. Finally, in telophase, the cells split into two sister cells.
Photosynthesis
Plants require water, sunlight, and carbon dioxide for photosynthesis. They obtain carbon dioxide from the air, water from precipitation absorbed by roots, and light from solar energy.