Characteristics of Living Organisms, Eukaryotes, Prokaryotes, Pathogens, and Levels of Organisation

Flashcards reviewing the characteristics of living organisms, eukaryotic and prokaryotic cell structures, pathogenic organisms, and biological levels of organisation.

What does the mnemonic acronym MRS C GREN represent in biology?

MRS C GREN stands for Movement, Respiration, Sensitivity, Control, Growth, Reproduction, Excretion, and Nutrition.

How do plants and animals differ in how they obtain nutrition?

Plants produce food (glucose and oxygen) using sunlight, carbon dioxide, and water through photosynthesis. Animals consume other living organisms, breaking down complex molecules via digestion to absorb nutrients into the bloodstream.

What is the word equation for aerobic respiration?

$$\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water}$$

In what form is energy transferred during cellular respiration?

Energy released during respiration is transferred in the form of ATP.

How does excretion differ from egestion in living organisms?

Excretion is the removal of toxic waste products originating from metabolic chemical reactions in cells. Egestion is the removal of undigested waste as faeces, originating from substances not absorbed during digestion.

What waste products are excreted by animals, and where do they originate?

Animals excrete carbon dioxide from aerobic respiration, water from respiration and other chemical reactions, and urea containing nitrogen from the breakdown of proteins.

How do the waste products excreted by plants change between day and night?

During the day, oxygen is excreted when the rate of photosynthesis exceeds respiration. At night, carbon dioxide is excreted when the rate of respiration exceeds photosynthesis.

What are the two systems used by animals to detect and respond to stimuli?

The nervous system (using receptors, neurones, effectors, and electrical impulses) and the endocrine system (using chemical messengers called hormones traveling in the blood).

What are phototropism and geotropism in plants?

Phototropism is a plant shoot's growth response towards light. Geotropism is a plant root's growth response to gravity, causing roots to grow downwards into the soil.

What is thermoregulation, and what is the optimum body temperature for humans?

Thermoregulation is the homeostatic control of internal body temperature, maintained at an optimum of $37\,^{\circ}\text{C}$.

How do plants control their internal temperature through homeostasis?

Plants use transpiration, in which water evaporates from stomata on the underside of the leaves, resulting in heat loss.

How do sexual and asexual reproduction differ regarding parent input and genetic identity of offspring?

Sexual reproduction involves two parents whose male and female gametes fuse, producing offspring with combined maternal and paternal DNA. Asexual reproduction involves one parent producing genetically identical clones.

What defines growth in living organisms?

Growth is defined as a permanent increase in size.

What primary cellular feature defines all eukaryotic organisms?

Eukaryotic cells contain a nucleus bounded by a distinct membrane.

What are the key characteristic features of organisms in the animal kingdom?

Animals are multicellular, have cells with a distinct membrane-bound nucleus, lack cellulose cell walls and chloroplasts, store carbohydrates as glycogen, usually have nervous coordination, and can move from place to place.

What are the key characteristic features of plants regarding cell walls, chloroplasts, and carbohydrate storage?

Plants are multicellular eukaryotes with cellulose cell walls and chloroplasts for photosynthesis, storing carbohydrates as starch or sucrose, and lacking nervous coordination.

What is the structural organization of multicellular fungi, and how do they obtain nutrients?

Multicellular fungi (such as Mucor) consist of thread-like hyphae organized into a network called a mycelium. They feed via saprotrophic nutrition by secreting extracellular digestive enzymes onto decaying organic matter and absorbing the digested molecules.

What material makes up fungal cell walls, and how do fungi store carbohydrates?

Fungi have cell walls made of chitin and store carbohydrates as glycogen.

Give examples of animal-like and plant-like protoctists.

Plasmodium is an animal-like protoctist that causes malaria. Chlorella is a plant-like protoctist that contains chloroplasts and carries out photosynthesis.

What structural features distinguish prokaryotic cells (such as bacteria) from eukaryotic cells?

Prokaryotes are single-celled, substantially smaller, lack a nucleus (genetic material is a single circular chromosome in cytoplasm), lack mitochondria and membrane-bound organelles, contain plasmids, and have peptidoglycan cell walls.

What are Lactobacillus bulgaricus and Pneumococcus?

Lactobacillus bulgaricus is a rod-shaped bacterium used in making yoghurt from milk. Pneumococcus is a spherical bacterium that acts as a pathogen causing pneumonia.

Why are viruses not classified as living organisms?

Viruses are not considered living because they do not carry out the eight life processes for themselves and can only reproduce by taking over a host cell's metabolic pathways.

What structural components form a typical virus particle?

A typical virus particle consists of nucleic acid (either DNA or RNA) enclosed in a protein coat, sometimes surrounded by an envelope.

What pathogen causes malaria in humans, and how is it transmitted?

Malaria is caused by Plasmodium falciparum, a pathogenic protoctist spread by mosquitoes.

What are the symptoms and long-term soil persistence of Tobacco Mosaic Virus (TMV)?

TMV causes a distinctive mosaic pattern of leaf discolouration by infecting chloroplasts, reducing photosynthesis and crop yield. The virus can stay in soil for about $50\,\text{years}$.

How does HIV affect the human body, and how can its progression be controlled?

HIV travels to lymph nodes and attacks cells of the immune system, eventually leading to AIDS if untreated. While there is no cure, antiretroviral drugs used early in infection can control virus progression.

What are the five levels of organisation in multicellular organisms?

The five levels are organelles, cells, tissues, organs, and organ systems.

Based on this diagram of a plant leaf, identify the levels of organisation for labels 1, 2, and 3.

Structure 1 is an organ (leaf), structure 2 is a cell (palisade mesophyll cell), and structure 3 is a tissue (upper epidermis).

Which organs comprise the human excretory system, and what waste products do they excrete?

The excretory system includes the lungs (excreting carbon dioxide and water), kidneys (excreting water, mineral ions, and urea), and skin (excreting water and mineral ions).