biology

Here’s a Biology practice question on ATP and energy for students preparing for the DAT and OAT. Before looking at the second image, see if you can identify why energy input is required to synthesize ATP from ADP and Pi. Then check Dr. Romano’s explanation. Free DAT Preparation Resources...

Here’s a Biology practice question on ATP and energy for students preparing for the DAT and OAT. Before looking at the second image, see if you can identify why energy input is required to synthesize ATP from ADP and Pi. Then check Dr. Romano’s explanation. Free DAT Preparation Resources...

Congratulations to Avi Agh, the winner of our 2026 Labor Day Giveaway! Avi selected the 2026 DAT Destroyer, our complete DAT science preparation book covering Biology, General Chemistry, and Organic Chemistry. Thank you to everyone who participated. Dr. Romano and I truly appreciate your...

Congratulations to Avi Agh, the winner of our 2026 Labor Day Giveaway! Avi selected the 2026 DAT Destroyer, our complete DAT science preparation book covering Biology, General Chemistry, and Organic Chemistry. Thank you to everyone who participated. Dr. Romano and I truly appreciate your...

Here is a Biology question for students preparing for the DAT and OAT. The greatest number of sexes will be demonstrated in which of the organisms shown? Choose your answer before checking the second slide for Dr. Romano's explanation. Free DAT and OAT study resources from Dr. Jim Romano...

Here is a Biology question for students preparing for the DAT and OAT. The greatest number of sexes will be demonstrated in which of the organisms shown? Choose your answer before checking the second slide for Dr. Romano's explanation. Free DAT and OAT study resources from Dr. Jim Romano...

Birds and dinosaurs provide an interesting way to review evolutionary history for the DAT and OAT. Test yourself with the question in the first image before checking Dr. Jim Romano's explanation in the second image. Keep practicing and keep Destroying! Free DAT & OAT Resources from Dr. Jim...

Birds and dinosaurs provide an interesting way to review evolutionary history for the DAT and OAT. Test yourself with the question in the first image before checking Dr. Jim Romano's explanation in the second image. Keep practicing and keep Destroying! Free DAT & OAT Resources from Dr. Jim...

Endocrine cells are not limited to the major endocrine glands. The stomach also contains enteroendocrine cells that secrete hormones involved in regulating digestion and other physiological processes. Give the problem a try before checking Dr. Romano’s explanation. Understanding the endocrine...

Endocrine cells are not limited to the major endocrine glands. The stomach also contains enteroendocrine cells that secrete hormones involved in regulating digestion and other physiological processes. Give the problem a try before checking Dr. Romano’s explanation. Understanding the endocrine...

Can you solve this DAT/OAT Biology problem? The loop of Henle is an important part of kidney physiology. Understanding how the descending and ascending limbs differ in their permeability to water and ions is an important concept for the DAT and OAT. Take a look at the nephron diagram and...

Can you solve this DAT/OAT Biology problem? The loop of Henle is an important part of kidney physiology. Understanding how the descending and ascending limbs differ in their permeability to water and ions is an important concept for the DAT and OAT. Take a look at the nephron diagram and...

Which nervous system structure is associated with the control of hunger? The hypothalamus acts as a major control center for hunger and energy balance. It processes hormonal and nutrient signals from the body that help regulate sensations of hunger and fullness. Give this DAT/OAT Biology...

Which nervous system structure is associated with the control of hunger? Give this DAT/OAT Biology question a try before checking Dr. Jim Romano’s solution. The hypothalamus acts as a major control center for hunger and energy balance. It processes hormonal and nutrient signals from the body...

How well do you know the defining characteristics of the phylum Chordata? This is one of those Biology concepts that appears simple at first but is tested repeatedly on both the DAT and OAT. A solid understanding of chordate characteristics helps you answer a wide variety of Biology questions...

Methanogens are one of the highest-yield microbiology topics tested on the DAT and OAT. These unique microorganisms produce methane (CH₄) and belong exclusively to the domain Archaea, not Bacteria or Eukarya. Test yourself with the question before looking at the solution on the second slide...

Methanogens are one of the highest-yield microbiology topics tested on the DAT and OAT. These unique microorganisms produce methane (CH₄) and belong exclusively to the domain Archaea, not Bacteria or Eukarya. Test yourself with the question before looking at the solution on the second slide...

How well do you know the defining characteristics of the phylum Chordata? This is one of those Biology concepts that appears simple at first but is tested repeatedly on both the DAT and OAT. A solid understanding of chordate characteristics helps you answer a wide variety of Biology questions...

Permutation problems reward students who identify the restriction before they begin counting. In this example, a sequence consists of three pentoses (5-carbon sugars) and five hexoses (6-carbon sugars), with the condition that a hexose must be placed on each end. Once those positions are...

Acute inflammation is one of the highest-yield Biology topics on the DAT and OAT. Students should understand the sequence of cellular events and be able to distinguish acute from chronic inflammation. One of the most commonly tested concepts is identifying the first leukocytes recruited to...

Acute inflammation is one of the highest-yield Biology topics on the DAT and OAT. Students should understand the sequence of cellular events and be able to distinguish acute from chronic inflammation. One of the most commonly tested concepts is identifying the first leukocytes recruited to...

Can you identify these leukocytes before looking at the answer? This DAT/OAT Biology question tests your understanding of neutrophils, one of the highest-yield immune system topics on the exam. To answer this question correctly, you should know that neutrophils: Contain microbicidal...

an you identify these leukocytes before looking at the answer? This DAT/OAT Biology question tests your understanding of neutrophils, one of the highest-yield immune system topics on the exam. To answer this question correctly, you should know that neutrophils: Contain microbicidal...

Can you identify the type of immunity illustrated in this classic DAT/OAT Biology question? Understanding the differences between innate immunity, active immunity, passive immunity, natural immunity, and artificial immunity is essential for the DAT and OAT. This is a high-yield topic that...

Can you identify the type of immunity illustrated in this classic DAT/OAT Biology question? Understanding the differences between innate immunity, active immunity, passive immunity, natural immunity, and artificial immunity is essential for the DAT and OAT. This is a high-yield topic that...

Fibroblasts are a classic DAT and OAT Biology topic that every student should master. They are the primary connective tissue cells responsible for synthesizing collagen and the extracellular matrix, making them essential for tissue repair and maintenance. In the attached slides, Dr. Jim Romano...

Fibroblasts are a classic DAT and OAT Biology topic that every student should master. They are the primary connective tissue cells responsible for synthesizing collagen and the extracellular matrix, making them essential for tissue repair and maintenance. In the attached slides, Dr. Jim Romano...

Enzymes and inhibitors are among the highest-yield Biology topics on the DAT and OAT. In this video, Dr. Jim Romano explains the key concepts you need to understand, including how different inhibitors affect enzyme activity and how these questions are commonly tested. Free DAT & OAT Study...

Enzymes and inhibitors are among the highest-yield Biology topics on the DAT and OAT. In this video, Dr. Jim Romano explains the key concepts you need to understand, including how different inhibitors affect enzyme activity and how these questions are commonly tested. Free DAT & OAT Study...

Can you identify the statement that is NOT a likely explanation for matriarchal leadership in sheep? This DAT/OAT Biology question examines animal behavior, herd dynamics, and evolutionary adaptations. Work through the choices before viewing the answer and explanation on the second slide...

Can you identify the statement that is NOT a likely explanation for matriarchal leadership in sheep? This DAT/OAT Biology question examines animal behavior, herd dynamics, and evolutionary adaptations. Work through the choices before viewing the answer and explanation on the second slide...

Annual growth rings (tree rings) are a classic Biology topic that tests your understanding of plant anatomy. The vascular cambium produces new secondary xylem inward each growing season. The varying rate of secondary xylem production during the seasons creates the annual growth rings seen in...

Every class is an opportunity to strengthen concepts, ask questions, and build the confidence needed for test day. At DAT Destroyer, students don't just memorize answers—they learn how to think through challenging Biology, General Chemistry, Organic Chemistry, and Quantitative Reasoning...

Every class is an opportunity to strengthen concepts, ask questions, and build the confidence needed for test day. At DAT Destroyer, students don't just memorize answers—they learn how to think through challenging Biology, General Chemistry, Organic Chemistry, and Quantitative Reasoning...

The reticuloendothelial system (mononuclear phagocyte system) is a high-yield Biology topic tested on both the DAT and OAT. In this lesson, Dr. Jim Romano explains the role of macrophages, phagocytosis, and immune system function, while highlighting the concepts students commonly miss on exam...

The reticuloendothelial system (mononuclear phagocyte system) is a high-yield Biology topic tested on both the DAT and OAT. In this lesson, Dr. Jim Romano explains the role of macrophages, phagocytosis, and immune system function, while highlighting the concepts students commonly miss on exam...

Congratulations to another outstanding OAT student! We're grateful that this student allowed us to share their experience anonymously to help encourage future optometry students. OAT Scores Academic Average: 370 (95th percentile) Total Science: 360 (88th percentile) Biology: 400 (99th...

Enrollment is now open for our Fall 2026 DAT and OAT Preparation Classes. For more than 35 years, Dr. Jim Romano has helped thousands of students prepare for the DAT and OAT through comprehensive study materials and live instruction. Our program features: Live online and in-person classes...

Understanding the cytochrome P450 (P450) enzyme system is essential for success on the DAT and OAT Biology sections. In this lesson, Dr. Jim Romano explains how the liver detoxifies drugs, toxins, and other foreign compounds through the P450 enzyme system. Instead of memorizing isolated facts...

Many students confuse D/L notation with the direction of optical rotation. These are different concepts and should not be used interchangeably. Mastering amino acid stereochemistry is essential for success on the DAT and OAT. Understanding the underlying concepts—not just memorizing facts—will...