6F: TYPES OF EXPERIMENTAL METHOD

in vivo experiments

refers to experiments conducted within a living organism

in vivo experiments

these studies involve testing or observing biological processes as they naturally occur in a whole organism, such as a human, animal, or plant.

Natural environment: Experiments are conducted in the living organism, maintaining the natural context for biological processes.

Complex interactions: In vivo studies capture the effects of complex interactions between various biological systems (e.g., organs, tissues, cells, hormones).

key features of in vivo experiments

• Test the effects of a new drug on a living animal

• Study disease progression in a human subject or measure physiological changes in plants under different environmental conditions

examples of in vivo experiments

• Realistic results: In vivo studies provide results that are more representative of what happens in nature because all of the organism's biological systems interact

• Applicability to human/animal health: These studies are crucial in medical research for developing treatments and understanding diseases as they occur in whole organisms

advantages of in vivo experiments

• Ethical concerns: There are ethical issues, especially when testing on animals or humans, and such studies require strict regulatory approval.

• Complexity: The biological systems are complex, making it difficult to isolate the effect of the studied variable

disadvantages of in vivo experiments

in vitro experiments

refers to experiments conducted outside a living organism, typically in a controlled laboratory environment such as a test tube, petri dish, or culture plate

in vitro experiments

these experiments often focus on studying cells, tissues, or molecules in isolation from the whole organism

• Artificial environment: The study occurs outside the living organism in a lab setting

• Simplified system: By isolating cells, tissues, or specific biological components, researchers can focus on the direct effects of variables on those components without interference from other biological systems

key features of in vitro experiments

• Testing the effect of a drug on cultured cells

• studying the behavior of proteins in a test tube

• examining DNA replication in controlled lab conditions

give me an examples of in vitro experiments

• Control over variables: In vitro experiments allow researchers to manipulate specific variables without the complexity of an entire organism, leading to clearer results for specific mechanisms

• Ethical considerations: Fewer ethical concerns compared to in vivo experiments since no whole organisms are used

advantages of in vitro experiments

• Lack of complexity: Since the experiment is conducted outside the organism, in vitro, results may not fully reflect how a process would occur within a living system

• Limited generalizability: The results of in vitro studies may not always be applicable to in vivo conditions, as they do not account for the interactions of complex biological systems

disadvantages of in vitro experiments

direct measurement

refers to the quantitative collection of data by directly observing or measuring the phenomenon under study rather than through indirect methods such as modeling or inference.

direct measurement

In scientific experiments, this can apply to both in vivo and in vitro settings, depending on the collected data type

• Immediate observation: The researcher directly observes or measures the variable of interest, such as temperature, pressure, concentration of a chemical, heart rate, or blood flow

• Accurate data collection: Instruments or tools (e.g., thermometers, spectrometers, or sensors) are used to record exact values without relying on estimates or proxies

key features of direct measurement

• Measuring an animal’s heart rate during an experiment (in vivo), using a spectrophotometer to measure the absorbance of a solution in a test tube (in vitro)

• directly measuring environmental factors like CO₂ levels in the air

examples of direct measurement

• precision: often more accurate and reliable, as they do not rely on assumptions or indirect calculations.

• Real-time data: allows for the immediate recording of experimental conditions or outcomes, providing real-time information

advantages of direct measurement

• Instrument dependence: The quality of direct measurements depends on the accuracy and calibration of the instruments used.

• Limited scope: Some variables or phenomena are difficult or impossible to measure directly, requiring indirect approaches

disadvantages of direct measurement

vivo studies

provide insights into how processes work within the complex interactions of a living organism.

vitro experiments

allow researchers to simplify and isolate processes to understand specific mechanisms.

direct measurement

ensures that the data collected, whether from in vivo or in vitro experiments, is precise and reliable

For instance, a researcher may start with in vitro experiments to explore a biological process in isolation and then conduct in vivo experiments to validate the findings in a living system. Direct measurement is used throughout these processes to collect accurate data.

how these three methods often complementary?

in vivo

where it takes place: in a living organism

in vitro

where it takes place: outside a living organism

direct measurement

where it takes place: in vivo or vitro

in vivo

focus: entire biological syystem

in vitro

focus: isolated biological components

direct measurement

focus: direct data collection

in vivo

examples: drug testing on animals, human trials

in vitro

examples: cell cultures, molecular biology

direct measurement

examples: measuring heart rate, enzyme activity

in vitro

strengths: highly controlled environment, ethical

direct measurement

strengths: accurate, real-time data

in vivo

limitations: ethical concerns, high complexity

limitations: