Regents Biology Review

Regents Biology Review: Key Ideas 1-3

Introduction

• This video is the first in a series of Regents Biology review videos.

• The content is designed to help students review essential information for the Regents Living Environment exam in New York State.

• It can also be used as a refresher for basic biology topics or for exam review in other states.

• Resources are linked in the video description, encouraging viewers to subscribe for more content.

Exam Overview

• The Regents Living Environment exam has four parts with a mix of multiple-choice and open-ended questions.

• The exam also tests laboratory skills and scientific inquiry.

• This video covers biology knowledge and content, focusing on key ideas one through three, which covers approximately half of the required biology content knowledge.

• The Regents website provides information about the exam format and types of questions.

Levels of Organization in Life

• Life is organized.

• A population is defined as a group of organisms of one species in one location.

• Populations can be categorized by their functions, such as in a food web.

Food Webs and Trophic Levels

• Organisms are categorized into trophic levels or energy levels based on their feeding habits.

• Producers (Autotrophs) generate their own food, usually from sunlight (photosynthesis) or chemical energy.

• Consumers (Heterotrophs) consume other organisms.

• Decomposers break down organic material from other organisms.

• Think of decomposers like nature's recyclers. When plants and animals die, decomposers (like bacteria and fungi) break them down. This puts important stuff, like nutrients, back into the soil, which then helps new plants grow. It's like they're cleaning up and feeding the plants at the same time

• A food chain illustrates one pathway of energy flow, while a food web shows interconnected food chains within an ecosystem.

Autotrophs vs. Heterotrophs

• Autotrophs (producers) can create their own organic molecules for food. Plants are autotrophic.

• Heterotrophs (consumers) must consume other organic compounds for food by consuming other organisms.

• Humans obtain nutrients by consuming other organisms or their products.

Trophic Pyramid

• The trophic pyramid consists of:

  • Producers at the bottom.

  • Primary consumers.

  • Secondary consumers

  • Tertiary consumers.

• Energy is lost at each level, typically as heat; up to 90% of energy can be lost when moving up a level.

• It is more efficient to consume organisms lower on the pyramid. An energy pyramid explains that it is more efficient to consume lower on the pyramid than it is to be a tertiary or quaternary consumer.

Ecosystems

• Ecosystems consist of biotic (living) and abiotic (non-living) factors.

• Interactions between these factors shape the ecosystem.

• Competition occurs between organisms and interactions between populations within an environment.

• Natural checks and balances maintain ecosystem stability over long periods, often hundreds or thousands of years.

• Populations usually reach a carrying capacity due to limited resources like food, water, and space.

• Sharp population declines may indicate disease, new predators, or invasive species.

Human Organization and Homeostasis

• Humans are complex organisms composed of molecules that form cells.

• Cells form tissues, tissues form organs, and organs form organ systems (e.g., digestive, circulatory, respiratory, excretory, immune).

• These systems perform life functions essential for survival.

• Specialized cells work together to perform specialized functions.

• Organisms maintain homeostasis (stable internal balance) to survive.

• Failure to maintain homeostasis can lead to disease or death.

• Examples of homeostasis:

  • Sweating when body temperature rises: the brain signals blood vessels to dilate and sweat glands to secrete fluid, cooling the body through evaporative cooling.

  • Shivering to generate heat when cold.

  • Ectotherms (e.g., lizards) move to warmer or cooler locations to regulate their temperature because they cannot regulate their temperature internally.

• Disruptions in body systems can disrupt homeostasis.

Cells and Organelles

• Cells have specialized structures called organelles, each with specific functions.

• Examples:

  • Mitochondria (energy production).

  • Ribosomes (protein synthesis).

  • Nucleus (DNA storage).

  • Vacuole (storage).

  • Cell membrane (controls movement of molecules in and out).

  • Plant cells also have a cell wall and chloroplast.

• Molecules are transported through diffusion. Larger organic molecules must be broken down before cells can use them.

Organelle Functions

• Mitochondria: The site of aerobic cellular respiration; sometimes simplified as an oval with a squiggle line, but can also be shown with inner folds or cristae.

• Chloroplast: The location of photosynthesis; more complex with stacks of thylakoids. Plants have cell wall and chloroplasts as well.

• Vacuole: Used for storage.

• Ribosomes: Used to make proteins.

• Nucleus: The storage site of DNA in eukaryotic organisms.

• Plasma membrane: A semi-permeable barrier made of phospholipids.

• Cell wall: For structure and support.

Eukaryotic vs. Prokaryotic Cells

• Eukaryotic Cells:

  • Complex.

  • Have membrane-bound organelles.

  • Larger.

  • DNA enclosed in a nucleus.

• Prokaryotic Cells:

  • Few organelles (mainly ribosomes).

  • No membrane-bound organelles.

  • Cell membrane, ribosomes, and DNA (not in a nucleus).

  • May have cilia or flagellum.

• Prokaryotic cells (bacteria, archaea) appeared first in Earth's history.

• Eukaryotic cells (animal and plant cells) are more complex.

Cell Communication

• Cells communicate through signaling pathways.

• Receptor molecules (proteins in the cell membrane) receive signals.

• Hormones released by glands are sent to cells for a specific reaction.

• The nervous system uses neurotransmitters as signaling molecules.

• Disruptions or blocked receptor molecules impair cell communication, affecting stability.

• Example: Caffeine blocks adenosine signaling, reducing sleepiness.

Single-Celled Organisms

• Single-celled organisms have specialized structures to perform tasks like movement (e.g., pseudopods).

Genes and Environment

• Traits are inherited through genes, but their expression can be modified by the environment.

• Identical twins separated at birth may develop different heights and weights due to varying diets, physical activities, and environmental factors.

• Most traits are influenced by multiple genes.

• Genes are sections of DNA that code for specific proteins.

• DNA (deoxyribonucleic acid) is a nucleic acid made of nucleotides (phosphate, sugar, and a base [A, T, G, C]). The order of these bases determines what proteins that DNA will code for, and those proteins will give us the traits that we have.

DNA Structure and Function

• All cells contain the same DNA, but different parts are activated in different cells.

• Analogy: DNA is like a cookbook; each cell has the same cookbook but uses different recipes.

• DNA consists of nucleotides with bases A, T, G, and C. Each base pairs with a complementary base on the other side of the DNA molecule.

• DNA is a double helix, with base pairs connected by hydrogen bonds.

  • A pairs with T.

  • G pairs with C.

• Mnemonic devices: "apple tree, good cookie" or "All teachers can go."

Example of Complementary Base Pairing

• If one strand of DNA is ATTGCG, the complementary strand is TAACGC.

Protein Synthesis

• DNA holds instructions for proteins.

• DNA is transcribed into mRNA (messenger RNA), which carries the code to ribosomes for protein synthesis.

  Protein synthesis. Transcription comes before translation. DNA turns into mRNA first, then mRNA makes a protein.

• Proteins are long molecules made of 20 different amino acids.

• All organisms share the same universal genetic code.

Genetic Engineering and Biotechnology

• Humans have used artificial selection and selective breeding for thousands of years to create new varieties of plants and animals.

• Genetic engineering manipulates genes in organisms.

• Gel electrophoresis (DNA fingerprinting) is used for forensic analysis, paternity testing, and studying evolutionary relationships.

• Transgenic organisms (plants, animals, bacteria) are created for agriculture and industry using genes from multiple organisms.

  • Example: BT corn with genes to fight off insects.

  • Bacteria modified to clean up oil spills.

Gel Electrophoresis

• DNA is negatively charged; DNA must be cut up with enzymes in special places. Then take our DNA, put it into specialized gel, and run an electrical current through it.

• DNA migrates towards the positive end of the gel, separating bands based on size.

• In gel electrophoresis, larger DNA fragments stay closer to the wells (at the top) because they have more difficulty moving through the gel, while smaller fragments move faster and farther, ending up closer to the bottom. This is because DNA is negatively charged; DNA must be cut up with enzymes in special places. Then take our DNA, put it into specialized gel, and run an electrical current through it. DNA migrates towards the positive end of the gel, separating bands based on size.

• Comparing DNA bands from a crime scene to suspects can identify matches.

Evidence for Evolution

• Biochemical evidence from gel electrophoresis helps determine DNA and protein similarities among organisms.

• This data constructs the tree of life and supports evolution, helping to illustrate how different organisms are related to each other and to give support for how evolution has happened.. Embryonic development, fossil evidence, morphological evidence (physical characteristics) are also used.

• Species evolve from earlier species; new combinations of genes or mutations are inherited and create variations in populations.

• Mutations (changes in DNA) can be caused by mutagens (radiation, chemicals).

• Mutations are only passed to offspring if they occur in sex cells.

Natural Selection and Adaptation

• Organisms better adapted to their environment are more likely to survive, reproduce, and pass on their genes.

• Example: in a population of bacteria, if some bacteria are naturally resistant to antibiotics, treating the population with antibiotics leaves only the resistant bacteria to survive and reproduce, creating an antibiotic-resistant population. In this example, the resistant bacteria were more fit.

• Genetic diversity within a species increases the likelihood of survival when environmental changes occur because there are more adaptive characteristics to support survival through hundreds, thousands, and millions of years.

• Adaptations can be behavioral, structural, or reproductive.

• Life first arose billions of years ago; multicellular organisms evolved later.

Phylogenetic Trees and Cladograms

• Phylogenetic trees (cladograms) compare evolutionary histories and relatedness among species.

• The number of branches between organisms indicates how closely related they are.

• Traits can be mapped on the tree, indicating when characteristics arose.

• Example: kangaroos and humans are more closely related because they have a more recent common ancestor than humans and sharks.

• Kangaroos and humans have mammary glands, while bullfrogs and sharks do not, based on where the trait appears on the tree.

Evolution

• There is no single "ultimately evolved" organism.

• Environments are constantly changing, and populations continue to evolve.

• Individuals do not evolve; populations evolve.

• Evolution is the change in allele frequencies over time.

• Extinction occurs when a species lacks sufficient adaptive characteristics for survival.

• Most species that have existed on Earth are now extinct, as evidenced by the fossil record.

Conclusion

• This review covered key ideas one through three and standard four of the Living Environment/biology curriculum in New York State.

• The video encourages viewers to stay tuned for the next part in the series and to like the video if it was helpful.