Untitled Flashcard Set

Introduction to Life Processes and the MRS C GREN Acronym

To be classified as a living organism, an entity must fulfill specific criteria that apply universally across all forms of life.

If an entity does not carry out all of these vital life processes simultaneously, it is categorized as either dead or a non-living particle/agent.

Viruses are explicitly cited as examples of non-living particles or agents because they do not independently perform these processes.

The eight characteristics of living organisms can be remembered using the acronym MRS C GREN:

M: Movement

R: Respiration

S: Sensitivity

C: Control

G: Growth

R: Reproduction

E: Excretion

N: Nutrition

Nutrition: Energy and Materials for Development

Nutrition is the process by which organisms obtain food to provide the energy and essential materials required for growth and development.

Energy derived from nutrition is fundamental to fueling other life processes, such as movement and excretion.

Nutrition in Plants (Producers):

Plants are classified as producers because they create their own food for energy.

They utilize sunlight, carbon dioxide, and water to produce glucose and oxygen through the chemical process of photosynthesis.

Chemical formula for photosynthesis: $6CO_2 + 6H_2O \xrightarrow{\text{Light Energy}} C_6H_{12}O_6 + 6O_2$

Nutrition in Animals (Consumers):

Animals are consumers, meaning they must ingest other living organisms (such as plants, other animals, or bacteria) to gain energy and nutrients.

In animals, large complex molecules are broken down into smaller, simpler molecules through the process of digestion.

These simpler molecules are absorbed into the bloodstream and transported to individual cells.

Once in the cells, these molecules are used for various processes:

Respiration (to release energy).

Growth.

Repair of tissues.

Examples of Nutritional Chains:

Energy from the sun is utilized by clover (a producer) via photosynthesis.

A grasshopper (a consumer) munches on the clover.

A bird (a consumer) eats the grasshopper.

Nutrition in Fungi:

Even fungi must consume external matter to take in food, aligning them with the requirement for nutrition.

Respiration: Chemical Energy Transfer

Respiration is a chemical process carried out inside the cells of all living organisms.

It is critical to distinguish respiration from the mechanical process of "gas exchange."

During respiration, energy is released from glucose and transferred in the form of ATP (Adenosine Triphosphate).

Types of Respiration:

Aerobic Respiration: Occurs in the presence of oxygen. The reaction produces carbon dioxide and water as waste products.

Chemical equation: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{ATP}$

Anaerobic Respiration: Occurs in the absence of oxygen.

Excretion: The Removal of Toxic Metabolic Waste

Chemical reactions taking place inside living cells are collectively described as metabolic reactions.

Metabolic reactions produce waste products, some of which are toxic and must be eliminated from the body to prevent harm.

Excretion is defined as the removal of toxic materials and substances from organisms.

Excretion in Animals:

Lungs: Excrete carbon dioxide ($CO_2$) and water vapor which result from aerobic respiration.

Kidneys: Excrete water, mineral ions, and urea. (Urea is a nitrogenous waste resulting from the breakdown of proteins).

Skin: Excretes water and mineral ions (predominantly through sweat).

Excretion in Plants:

Plants excrete oxygen as a byproduct of photosynthesis.

Plants excrete carbon dioxide as a byproduct of respiration.

The balance of excretion shifts based on the time of day:

At Night: The rate of respiration exceeds the rate of photosynthesis, causing $CO_2$ to be excreted.

During the Day: The rate of photosynthesis exceeds the rate of respiration, causing oxygen ($O_2$) to be excreted.

Sensitivity: Response to Surroundings

Sensitivity refers to an organism's ability to detect and respond to stimuli in its surroundings, which maximizes the chances of survival.

Sensitivity in Animals:

The Nervous System: Utilizes receptors, neurons, and effectors to detect and respond to stimuli via electrical impulses. Components include the Central Nervous System (CNS), Peripheral Nervous System (PNS), the brain, the spinal cord, and various nerves.

The Endocrine System: Facilitates responses using chemical messengers called hormones. These travel through the blood to target organs. Glands involved include the pituitary gland, adrenal gland, pancreas, testes, and uterus.

Sensitivity in Plants:

Responses are controlled by chemicals and are typically slower than animal responses.

Geotropism: A plant's response to gravity, which ensures roots grow downward into the soil.

Phototropism: A plant's response to light, which causes the shoot to grow toward the sunlight.

Movement and Locomotion

Movement is defined as an action by an organism causing a change in position or place.

Locomotion: The specifically identified movement of an entire organism from one place to another.

Plant Movement: While plants generally cannot move from place to place, they can change their orientation. For example, sunflowers track the sun's position and adjust their orientation throughout the day.

Control and Homeostasis

Organisms must control their internal environment to maintain conditions within specific required limits, a process known as homeostasis.

Thermoregulation: The control of body temperature.

The optimum human body temperature is approximately $37\,^\circ\text{C}$.

If temperature increases (e.g., during exercise), control mechanisms like sweating or vasodilation are initiated to return the temperature to the optimum level.

Osmoregulation: The control of internal water levels.

Control in Plants:

Plants use transpiration to maintain a suitable temperature. Water evaporates from the stomata (located on the underside of the leaf), resulting in heat loss.

Reproduction: Ensuring Survival of the Species

Reproduction is the process leading to the production of more of the same kind of organism, essential for the survival of populations and the species.

Sexual Reproduction:

Involves the fusion of male and female gametes.

In Humans: The male gamete is the sperm; the female gamete is the egg (ovum).

In Plants: The male gamete is found in pollen grains; the female gamete is the ovule.

Fusion creates a zygote, which develops into an embryo.

The DNA of the offspring is a combination of maternal and paternal DNA.

Asexual Reproduction:

Involves only one parent and produces an exact genetic clone through mitosis.

The DNA of the offspring is identical to the parental DNA.

Examples: Bacteria, amoeba, and plants (via natural runners or artificial cuttings).

Growth and Development

Growth is defined as a permanent increase in size.

Growth in Animals: Individual organisms grow larger between the zygote and adult stages, often involving changes in body proportions and shape.

Growth in Plants: Plants continue to grow larger throughout their entire life cycle, producing new shoots, leaves, and branches year after year.