Characteristics of life

Metabolism

Cellular organization

Homeostasis

How do we know that something is alive?

Characteristics of life

Adapatation through Evolution

Reproduction

Response to stimuli

Growth and development

RAQUEL SAN MARTÍN Science department, Compañía de María Logroño

Bibliography

CELLULAR ORGANIZATION

Living things are made of cells

Unicellular

Multicellular

REPRODUCTION

Reproduction is the process by which living things give rise to offspring.

SEXUAL

ASEXUAL

SEXUAL REPRODUCTION

Characteristics

Two parents are involved (both male and a female). Gamete (reproductive cells) formation and fertilization take place. The whole process is slow and lengthy. Variation occurs; offspring are different from parents, genetically and physically.

ASEXUAL REPRODUCTION

Characteristics

Single parent involved. No fertilization or gamete formation takes place. This process of reproduction occurs in a very short time. The organisms multiply and grow rapidly. The offspring is genetically similar.

TYPES OF ASEXUAL REPRODUCTION

Binary fission

Multiple fission

The nucleus of a cell divides multiple times creating lots of cells.

One cell splits into two cells of similar size.

Budding

One cell splits into two of differente size.

(ENERGY PROCESSING)

METABOLISM

Life depends on an enormous number of interlocking chemical reactions. These reactions make it possible for organisms to do work—such as moving around or catching prey—as well as growing, reproducing, and maintaining the structure of their bodies. Living things must use energy and consume nutrients to carry out the chemical reactions that sustain life. The sum total of the biochemical reactions occurring in an organism is called its metabolism.

Autotrophic organisms

All organisms use a source of energy for their metabolic activities. Some organisms capture energy from the sun and and inorganic matter and convert it into chemical energy in food (organic molecules) (autotrophs through photosynthesis); others use chemical energy in organic molecules they take in as food (heterotrophs).

Heterotrophic organisms

HOMEOSTASIS

All living things are able to maintain a more-or-less constant internal environment. They keep things relatively stable on the inside regardless of the conditions around them. The process of maintaining a stable internal environment is called homeostasis. Human beings, for example, maintain a stable internal body temperature. If you go outside when the air temperature is below freezing, your body doesn’t freeze. Instead, by shivering and other means, it maintains a stable internal temperature.

GROWTH & DEVELOPMENT

Organisms grow and develop following specific instructions coded for by their genes. These genes provide instructions that will direct cellular growth and development, ensuring that a species’ young will grow up to exhibit many of the same characteristics as its parents.

RESPONSE TO STIMULI

Complex coordination systems

Single cell coordination systems

• A STIMULUS is a change in the environment (either external or internal) that is detected by a receptor
• Receptors transform environmental stimuli into electrical nerve impulses.
• These impulses are then transmitted via neurons to the central nervous system where decision-making occurs
• When a response is selected (consciously or unconsciously), the signal is transmitted via neurons to effectors
• Effectors are organs (either muscles or glands) that produce a response to a stimulus
• A response is a change in the organism resulting from the detection of a stimulus

Even tiny bacteria can move toward or away from chemicals (a process called chemotaxis) or light (phototaxis). Movement toward a stimulus is considered a positive response, while movement away from a stimulus is considered a negative response. Picture: Salmonella Typhimurium (red) invading cultured human cells.

Organisms respond to diverse stimuli. For example, plants can bend toward a source of light, climb on fences and walls, or respond to touch. Picture: Mimosa pudica

ADAPTATION THROUGH EVOLUTION

Evolutionary adaptation, or simply adaptation, is the adjustment of organisms to their environment in order to improve their chances at survival in that environment. All living things adapt to external pressures, and evolve because of them. Adapting is much like responding to a stimulus in the environment, but takes it to the next level. Although scientists discussed adaptation prior to the 1800s, it was not until then that Charles Darwin and Alfred Russel Wallace developed the theory of natural selection. Descendants from individuals that are more highly adapted to its environment are more likely to survive. Their genes are “selected for” by the external pressures of the environment and transferred to the following generations.

Some creatures, such as this leafy sea dragon fish (Phycodurus eques) have evolved adaptations that allow them to blend in with their environment (in this case, seaweed) to avoid the attention of hungry predators. PHOTOGRAPH BY PAUL ZAHL https://education.nationalgeographic.org/resource/adaptation/

Bibliography

• NASA
• https://astrobiology.nasa.gov/education/alp/characteristics-of-life/
• Lumen learning
• https://courses.lumenlearning.com/suny-wmopen-biology1/chapter/the-characteristics-of-life/

• Study. com
• https://study.com/academy/lesson/8-characteristics-of-life-in-biology.html
• Amoeba sisters
• https://youtu.be/cQPVXrV0GNA?si=0Temkox_8RMNExtl
• National Geographic
• https://education.nationalgeographic.org/resource/adaptation/
• Bioninja
• https://ib.bioninja.com.au/standard-level/topic-6-human-physiology/65-neurons-and-synapses/stimulus-response.html
• Wikipedia images
• https://en.wikipedia.org/wiki/Salmonella