What cellular evidence do we have to construct evolutionary trees and believe that all life on Earth shares a common ancestry?
Learn about the interaction between chemical messages and their target cells in this video about hormone action.
Introduction to cellular respiration, including glycolysis, the Krebs Cycle, and the electron transport chain. Created by Sal Khan.
Introduction to cellular respiration, including glycolysis, the Krebs Cycle, and the electron transport chain. Created by Sal Khan.
Introduction to Cellular specialization.
How homologous chromosomes exchange fragments in prophase I. Tetrads, chiasmata, and alleles.
Overview of DNA transcription, translation, and replication during mitosis and meiosis. Learn about chromosomes, chromatids, and chromatin.
Introduction to the circulatory system and the heart.
The topic of this video module is how to classify animals based on how closely related they are. The main learning objective is that students will learn how to make phylogenetic trees based on both physical characteristics and on DNA sequence. Students will also learn why the objective and quantitative nature of DNA sequencing is preferable when it come to classifying animals based on how closely related they are. Knowledge prerequisites to this lesson include that students have some understanding of what DNA is and that they have a familiarity with the base-pairing rules and with writing a DNA sequence.
This variation on the classic bird beak activity demonstrates variation of beak size within a population and shows how the proportion of big-, medium-, and small-beaked birds changes in response to the available types of food. The birds with binder clip beaks live in Clipland where the large population becomes divided into two smaller populations by a mountain range. Popcorn, lima beans and marbles are the three types of food available in the two areas. Food is spread out for the birds to eat and then after 15 seconds it is counted to see whether birds have gathered enough food to survive. The big billed birds need to eat more than the medium and small billed birds to survive and each bird needs to eat more than the minimum amount of food for survival to be able to reproduce. Four years pass during the simulation and students are asked to describe what happened to the Clipbird populations and what they think caused the changes. A link to Rosemary and Peter Grants research on finch populations in the Galapagos is identified for those teachers who want to connect the simulation to a real life example.
In complete dominance, only one allele in the genotype is seen in the phenotype. In codominance, both alleles in the genotype are seen in the phenotype. In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype.
In this video segment from Nature, scientists work to discover why bees are disappearing.
Comparison of the processes of mitosis and meiosis. Mitosis produces two diploid (2n) somatic cells that are genetically identical to each other and the original parent cell, whereas meiosis produces four haploid (n) gametes that are genetically unique from each other and the original parent (germ) cell. Mitosis involves one cell division, whereas meiosis involves two cell divisions.
Seeing how an inhibitor can "compete" for an enzyme with the intended substrate.
Students will construct a model of the carbon cycle to explore the cycling of matter in decomposition. Students will design a process to compost food waste and recycle products used during lunchtime to reduce the amount of garbage the school produces.
A concentration gradient occurs when the concentration of particles is higher in one area than another. In passive transport, particles will diffuse down a concentration gradient, from areas of higher concentration to areas of lower concentration, until they are evenly spaced.
Concepts of Biology is designed for the introductory biology course for nonmajors taught at most two- and four-year colleges. The scope, sequence, and level of the program are designed to match typical course syllabi in the market. Concepts of Biology includes interesting applications, features a rich art program, and conveys the major themes of biology.
Seeing how light energy can excite electrons which can be used to create ATP and NADPH (with oxygen as a byproduct).
In this activity, students examine how to grow plants the most efficiently. They imagine that they are designing a biofuels production facility and need to know how to efficiently grow plants to use in this facility. As a means of solving this design problem, they plan a scientific experiment in which they investigate how a given variable (of their choice) affects plant growth. They then make predictions about the outcomes and record their observations after two weeks regarding the condition of the plants' stem, leaves and roots. They use these observations to guide their solution to the engineering design problem. The biological processes of photosynthesis and transpiration are briefly explained to help students make informed decisions about planning and interpreting their investigation and its results.
Covalent bonds involve the sharing of electron pairs between atoms. Electron pairs shared between atoms of equal or very similar electronegativity constitute a nonpolar covalent bond (e.g., Hƒ??H or Cƒ??H), while electrons shared between atoms of unequal electronegativity constitute a polar covalent bond (e.g., Hƒ??O). Created by Sal Khan.