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Giraffes evolved their long necks through natural selection. Millions of years ago, all giraffes had short necks. Some giraffes were a little bit taller than others, which meant they had variation. Because the taller giraffes could reach leaves that were higher on the trees more easily, they had the advantage of eating more food. Since the shorter giraffes couldn't reach the leaves from the tall trees, they weren't getting enough food, which resulted in them dying. The taller giraffes survived and allowed their offspring to inherit their slightly longer necks. As the years passed, all the giraffes had slightly longer necks, but because of the variation between them, some still had longer necks than the others. Eventually, their offspring inherited the longer necks. This process of natural selection repeated itself, causing a gradual evolution. After millions of years, all the giraffes had very long necks.

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Euglena is a unicellular organism that is found in the aquatic habitat. It is generally green in color due to the presence of chloroplasts. Euglena's internal structure is similar to that of a typical plant and animal cell, containing major parts such as cytoplasm, chloroplasts, mitochondria, smooth and rough endoplasmic reticulum, and a nucleus. Euglena moves forward and backward using a structure called a flagellum. Because of its eyespot movement, it's able to detect sunlight and produce food through photosynthesis. Euglena eats by having a mix of both autotrophic and heterotrophic modes. Euglena can also reproduce during the free-flowing stage by the asexual method, which is known as binary fission.

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What is Euglena

Euglena is a motile, single-celled (unicellular) organism that is commonly found in aquatic habitats. They were among the first organisms in the kingdom Protista to be seen under the microscope, looking like a tiny particle making small movements in the water. Euglena is generally green in color due to the presence of chloroplast, the organelle that helps them to perform photosynthesis.

Unlike the photosynthetic group, there is a parasitic group of Euglena that causes serious blood and tissue diseases such as African sleeping sickness and leishmaniasis in humans.

Euglena Image

Where do Euglena Live

Over 1000 different Euglena species are found infreshwater and saltwater habitats such as ponds, lakes, streams, rivers, and waterlogged areas like marshes.

Scientific Classification

Structure

Euglena is an elongated or spindle-shaped cellwith a size around 15-500 x 10⁻⁶ m.

Parts

Euglena

The internal structures found in a typical photosynthetic Euglena are as follows:

1. Pellicle: A thin, flexible membrane that supports the plasma membrane and helps them to change shape

2. Plasma Membrane: The selectively permeable membrane that protects the inner content of the cell from the outside environment

3. Cytoplasm: A jelly-like substance distributed throughout the cell that contains all the cell organelles

4. Chloroplast: Contains the green pigment chlorophyll that helps them to produce food using sunlight by photosynthesis

5. Nucleus: A membrane-bound organelle that contains the genetic material, DNA. It also contains a distinct nucleolus that contains RNA and helps the cell to synthesize proteins

6. Mitochondria: The energy-producing organelle that forms ATP. All cellular activities such as movement and reproduction are performed using the mitochondrial energy source

7. Ribosomes: Consists of RNA and proteins, and are responsible for producing all cellular proteins

8. Golgi Apparatus: Manufactures, stores, and transports large molecules such as carbohydrates and proteins within the cell

9. Endoplasmic Reticulum: The extensive network of membranes that helps to package and transport proteins to different organelles.It is of two types: rough endoplasmic reticulum (RER) - containing ribosomes attached to it; and smooth endoplasmic reticulum (SER) - devoid of ribosomes

10. Lysosomes: Small membrane-bound organelles filled with hydrolytic enzymes that break down large molecules such as carbohydrates, fats, and proteins

11. Contractile Vacuole: It maintains the water and salt balance within the cell

12. Reservoir: The inward pocket present near the base of the flagella where contractile vacuole dispels excess water

13. Flagellum: A long whip-like structure attached externally to the cell body that helps in cell movement. An amoeba contains two flagella, a short one that does not protrude out of the cell, and a long one that helps in swimming

14. Eyespot: A region that is highly colored and contains red-colored carotenoid pigments that help in the detection of light. It is sometimes called a stigma

15. Photoreceptor: Also known as the paraflagellar body, it is the light-sensitive region located near the flagellum that helps to detect light. It also helps in their movement towards and away from light stimuli, a process known as phototaxis

16. Paramylon: They are stored starch-like carbohydrate granules composed of glucose produced during photosynthesis. Paramylon enables the organism to survive in low-light conditions when photosynthesis is not possible by acting as the food reserve for the cell. When the paramylon is enclosed in a sheath of polysaccharide, it is called the paramylon sheath of pyrenoid.

Characteristics

How Is Euglena Similar to Plants

It is unique as it shows the features of both plant and animal cells. Like plant cells, some Euglena species are autotrophs and thus have the ability to use sunlight to prepare their food. However, others show features of an animal cell as they move from one place to another to acquire food from the environment.

How do They Move

Euglena moves forward and backward (bidirectional movement) using a long whip-like structure called a flagellum that acts like a little motor. The other part that plays a vital role in giving a sense of direction to its movement is the eyespot that helps to detect sunlight and produce food by photosynthesis. This is how Euglena responds to stimuli and performs the movement.

How Do Euglena Eat

It exhibits a mixotrophic mode of nutrition that uses a mix of both autotrophic and heterotrophic modes. While the photosynthetic species are autotrophs, others are found to be heterotrophs that obtain nutrients in the form of bacteria and algae through absorption by phagocytosis.

How Do They Respire

Euglena takes in free oxygen dissolved in water and breathe out carbon dioxide by diffusion through the pellicle and thus have ecological importance in purifying the atmosphere.

How do Euglena Reproduce

Most of the Euglena life cycle consists of a free-flowing stage and a non-motile stage. During the free-flowing stage, Euglena reproduces by an asexual method known as binary fission, where the parent cell divides equally to form two equal daughter cells.When the growth conditions become unfavorable, the cells of Euglena enclose themselves within a thick-walled protective covering called a cyst. This is the characteristic of their non-motile stage.

Some Euglena species also reproduce by forming reproductive cysts. During this period, they discard their flagella and become enveloped in a gelatinous, gummy substance to form reproductive cysts. Individual cysts then undergo binary fission to produce as many as 32 or more identical daughter- Euglena cells. When the conditions become favorable for growth, these daughter cells become flagellated and are released from the gelatinous mass to form actively dividing reproductive cells.
They have some other characteristic features, including the following:

Lack a cell wall

Require organic nutrients and vitamins such as vitamin B12 for their growth and development

Some species contain vitamin E (⍺-tocopherol) and high content of astaxanthin in their cell

Some species produce an alkaloid known as euglenophycin, which is found to kill fishes

FAQs

References

Article was last reviewed on Saturday, July 4, 2020

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Euglena: Definition, Structure, & Characteristics with Diagram

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Euglena is a motile, single-celled (unicellular) organism that is commonly found in aquatic habitats. They were among the first organisms in the kingdom Protista to be seen under the microscope, looking like a tiny particle making small movements in the water.

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Echinodermata include species such as sea stars and sea urchins. These organisms have spiny skin. They are symmetrical and are bilateral, sharing early embryonic stages with other organisms. Echinodermata have three germ layers. They have complete digestion, meaning they have a separate opening, one for the mouth and one for the anus. Because they have two openings, they can be classified as either a protostome or a deuterostome. All echinoderms move through a water vascular system, utilizing tubes to navigate through seawater. For example, a sea star suck in water through a sieve plate, filtering out anything bad. The water then travels through the radial canal, going down each arm of the sea star and filling the tubes, which are called impula. The muscles squeeze the water, and that gets pushed out, allowing the sea to move in any direction. Radial symmetry requires a lot of work to move in a particular direction, since there is no forward, backward, or side-to-side movement; it's equal in all directions. As a result, it causes them to move slowly, yet with equal momentum in any direction.

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Daily, we encounter both monocots and dicots. We encounter monocots daily in the form of grass and grains, which are commonly found in lawns and fields. Monocots have a fibrous root system and parallel-veined leaves, which play a crucial role in the photosynthesis process. Monocots also only contain one cotyledon. These plants are essential for agriculture and landscaping. For dicots, such as roses, daffodils, and sunflowers, they are mainly found in places like parks or gardens. Dicots contain two cotyledons. These plants are known for their taproot systems and branched, veined leaves, which also contribute to the photosynthesis process. Some of these plants play a vital role in our daily lives by providing food and shelter, as well as enhancing our surroundings.

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Homeostasis is your body's way of maintaining a stable internal environment despite changes in the external environment. It ensures that temperature, blood pressure, hydration, and pH remain within a healthy range. The hypothalamus in the brain acts as a command center that communicates with organs and glands to release hormones or trigger responses that restore balance. It works based on negative and positive feedback loops. Negative loops are the primary mechanism that reverses changes, such as sweating when hot or shivering when cold. Positive feedback loops are less common but occur in processes such as having contractions during childbirth. Positive feedback loops amplify changes until a goal is reached. Homeostasis is essential for survival, and any disruptions can lead to an illness or disease.

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Homeostasis is how your body maintains internal balance so its internal systems can run as effectively as possible.

What is homeostasis?

Homeostasis is how your body regulates your internal systems so they function correctly. Your body works best when its internal environment - including things like temperature or oxygen levels - is just right.

The term homeostasis comes from two ancient Greek words meaning "equal" and "holding still." In other words, homeostasis means reaching and maintaining a state of balance. In this context, balance isn't about keeping you from toppling over. It's about having the right balance of everything you need.

Balance is key because too much of even the most essential things can be harmful. For example, everyone knows that water and oxygen are good things, and you need them to survive. But drinking too much water too quickly can cause hyponatremia. And breathing pure oxygen for too long can cause oxygen toxicity. Both of those conditions can be deadly.

How does homeostasis work?

Homeostatic processes are automatic, and a specific part of your brain, the hypothalamus, runs them. There are two main ways that homeostasis happens:

Negative feedback

Positive feedback

Negative feedback homeostasis

Negative in this context doesn't mean bad. It means your body senses a change and tries to counteract or reverse the unwanted change. Most homeostatic processes in your body rely on negative feedback.

Examples of negative feedback homeostasis include:

Blood pressure. Your blood pressure keeps blood flowing up toward your head against the pull of gravity.

Body temperature. If you're too hot, your body makes you sweat to cool you down. If you're cold, your body makes you shiver to generate heat. These are examples of thermal (temperature) homeostasis.

Fluid balance. If you drink too much water, you'll soon feel the urge to pee to get rid of the extra fluid.

Oxygen levels. Your heart and breathing rates increase and decrease depending on how active you are. That's an example of respiratory and circulatory homeostasis.

Positive feedback homeostasis

Positive feedback homeostasis means the processes add to themselves and get stronger. That will keep on happening until the initial cause is gone.

Examples of positive feedback homeostasis include:

Labor and delivery. When labor starts, your cervix starts to stretch, which triggers nerve signals that go to your brain. Your brain releases the hormone oxytocin, which causes uterus contractions. The more your cervix stretches, the more oxytocin your brain releases and the stronger the contractions get. That stops once delivery is complete and your cervix returns to its normal size.

Hemostasis (blood clotting). When you have a wound that bleeds, clotting factors in your blood activate to seal the wound. They also call for reinforcements, summoning even more clotting factors. They'll keep on calling for more clotting factors until the bleeding stops.

Immune responses and inflammation. When you have an infection or injury, your immune system causes inflammation at that site. Inflammation is your body's way of shining a spotlight on a specific place so immune cells know exactly where to go. And immune cells at the scene will keep inflammation going as long as they need more help.

Why is homeostasis important?

You can't survive without homeostasis and the processes that drive it. And every disease or medical condition involves a disruption of homeostasis.

When you get hurt or sick, your body adjusts its homeostatic processes so you can recover. That's why you get a fever with infections or your blood clots when you have a bleeding wound.

Chronic conditions happen when something goes wrong and your homeostatic processes can't adjust enough to make up for it. For example, high blood pressure (hypertension) happens when your body can't keep the pressure within a healthy range. Osteoporosis happens when your bones lose calcium faster than your body can replace it.

Some diseases happen because homeostatic processes malfunction and make things worse. Examples include:

Allergic reactions. Allergies happen when your immune system reacts to something that it thinks is a threat. Mild allergies may just be unpleasant. But if the reaction is too strong, that homeostatic process can be dangerous. For example, a bee sting causes brief pain and mild swelling for most people. But a sting can cause deadly anaphylaxis for someone with an allergy.

Autoimmune diseases. These happen when your immune system malfunctions and mistakenly attacks part of your own body. The reaction itself would likely be normal and healthy if the target were an infection or injury instead of your own healthy tissues.

Cytokine release syndrome (CRS) or sepsis. Immune system reactions naturally strengthen with time and will stop once the initial cause is gone. But those processes can rapidly become dangerous if your immune system reacts too strongly early on. That's why CRS and sepsis can become deadly so quickly.

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Homeostasis is a state of balance, and your body regulates its own systems to reach and maintain it. It's key to how all your body systems work.

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Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that can affect multiple organ systems and is often difficult to diagnose due to various symptoms. In the article, lupus, specifically systemic lupus erythematosus, is a case study of a 12-year-old girl whose unusual presentation of splenic infarction led to her diagnosis. The patient suffered from fevers, nausea, body aches, and left abdominal pain for several weeks. Lab tests showed anemia, thrombocytopenia, and proteinuria. Further testing later confirmed SLE and antiphospholipid syndrome. The patient underwent treatments such as steroids, hydrochloroquine, mycophenolate mofetil, plasmapheresis, and cyclophosphamide. After the intensive treatments, the patient stabilized and showed no significant symptoms with normal lab values. Splenic infarction in children should prompt evaluation for serious systemic diseases, such as SLE.

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The savanna biome is one of the most fascinating and diverse ecosystems on Earth. The savanna biome is a warm, grassy biome with scattered trees and two distinct seasons of wet and dry. During the wet season, plants thrive while the dry season brings droughts and fires that help renew the land. Both are essential for maintaining the balance of the ecosystem. The vegetation is mainly tall grasses and drought-resistant trees, such as acacias and baobabs, which have adapted to survive harsh conditions. The savannas are home to iconic wildlife, including elephants, lions, and giraffes, as well as birds, reptiles, and various insects. Savannas are found in Africa, South America, India, and Australia, each with its own unique species and adaptations. Despite their differences, all savannas share the common thread of being ecosystems built on adaptation, balance, and survival.