Because protists are eukaryotic creatures, they contain a nucleus. Protist cells usually have a single nucleus (they are mononucleate). Many protists, on the other hand, are multinucleated, meaning they have several nuclei. The protist nucleus, like other eukaryotic cells, holds the cell’s DNA, which regulates all the cell’s processes.
Which Organelles Are Found in Protist Cells?
Protists are eukaryotic creatures with membrane-bound organelles, unlike prokaryotes. A nucleus, as well as other features, including the endoplasmic reticulum and Golgi apparatus, are found in all protists. In addition to mitochondria, many protists have digesting vacuoles and chloroplasts. A cell wall may be found in both plant-like protists (algae) and fungi-like protists (moulds).
Protist Definition
Protists are eukaryotic creatures that are not plants, animals, or fungi that are loosely linked and typically unicellular. Because no single attribute, like the history of evolution or morphology, is shared by all of these animals, they are informally classified as protista. As a result, protists no longer have a formal classification, and various individuals exhibit varied degrees of similarity with organisms from all five eukaryotic kingdoms. However, it is still used to designate eukaryotic microscopic creatures as a word of convenience.
Originally, bacteria and fungi were included in this category, but it is now limited to organisms with a clearly defined nucleus and complicated cellular organization. There is no tissue-level organisation.
Protists History of Classification
Protists are a diverse group of living creatures that considerably exceed viruses and bacteria in terms of species biodiversity. There are about 3 times as many unknown protists as characterised ones, according to estimates. Their functional variety, as well as the global character of the niches they occupy, makes them critical for biodiversity conservation and preservation.
Ernst Haeckel initially classified protists as a category of creatures during the 1860s, taking the term protistos from the Greek word, which means “first.” Everything was first utilised to denote that these creatures were most likely primordial plant and animal forms. This expression emerged with the invention of the microscope and the finding of a large range of microbes.
The use of DNA sequencing as well as molecular genetics has made it simpler to identify evolutionary pathways and connections among species. This has also led to protist redistribution across the other five eukaryotic kingdoms. Some experts, on the other hand, categorise them according to their ultrastructure and biochemistry. Even as new techniques for studying phylogenetics emerge, the classification of protists remains an important topic of research.
Characteristics of Protists
Protists have a diverse range of eating behaviours, reproductive cycles, and movement styles. Some are autotrophs, converting sun energy into simple carbs by utilising pigments. Others, such as amoeba, are heterotrophs who feed on other creatures. In reaction to the environment, several species are being found to alter their autotrophic to heterotrophic dietary habits.
They can also be found in almost every biological niche, from hot springs to polar ice caps, swimming pools to mosquito guts. Some of these may even be found at geothermal vents in the ocean depths.
Most protists have mitochondria and a well-defined cellular structure. Rarely do cells organise into larger structures, though. Yet macroscopic species such as giant kelp, which may grow to be tens of metres long, are made up of enormous clonal aggregations of fully functioning and self-contained complex cells. Cells, as well as the creation of tissues and organs, lack specialisation. Polymorphy happens when a protist appears as a single cell at one stage in its life span and as a clonal aggregation at a later moment. This is one of the main reasons why large kelps are not designated plants.
The most common methods of reproduction are binary fission and budding, enabling the continuation of certain customizations. When sexual reproduction does occur, however, it may take several forms, including self-fertilization and cross-fertilization. Plasmodium, the parasite that causes malaria, its life cycle includes both an asexual phase and a sexual phase. Many protists are thought to be capable of sexual reproduction.
Types of Protists
The classification of protists is founded on their shape, size, nuclear structure type and amount, cytoplasmic organelles, the existence of endo-or exoskeleton components, etc. However, because of their diversity and uniqueness, informal classification is frequently focused on nourishment and movement.
Autotrophs
Although autotrophic, non-motile protists lack higher degrees of tissue organisation, they are frequently compared to plants. This group is thought to be responsible for almost 40% of all photosynthetic activity on the planet. The pigments employed in photosynthesis, such as chlorophyll (green algae), fucoxanthin (brown algae), and phycoerythrin (red algae), may further distinguish these species. Along with chlorophyll, Numerous of these are accessory colourants.
Heterotrophs
Heterotrophic and motile protists exist. They are divided into groups based on how they move. Pseudopodia, or “false feet,” are used by some, such as amoeba, whereas flagella or cilia are used by others. In many environments, these free-living protists are among the most important bacterial eaters and contribute to species diversity.
Fungi were assumed to be protists that degrade organic matter.
Examples of Protists
Protists are varied and may be found in a wide range of environments, frequently serving as primary producers or consumers at the bottom of the energy pyramid.
Giant Kelp
Giant kelps are a kind of autotrophic algal protist that may grow to create vast underwater forests. In addition to chlorophyll, they contain fucoxanthin pigments, which contribute to their brown hue. They live in shallow seas with enough light and nutrients to support a complex ecology.
Paramecium
These bacteria are common in aquatic basins, from sluggish ponds to the open ocean. They are often employed to study sexual reproduction. They have a lot of cilia and move in a coordinated way with them.
When exposed to intense environmental stress, they have been seen to shed their slipper-like appearance.
Parasitic Protists
Numerous parasitic protists are free-living and may harm animals and crops. Malaria is caused by Plasmodium in humans and simians. Amoebic dysentery is caused by Entamoeba histolytica. Water moulds like Phytophthora infestans (the reason for the Irish Potato Famine) and Plasmopara viticola have wreaked havoc on crops.
Related Biology Terms
- Algae are a broad group of photosynthetic eukaryotes that primarily inhabit aquatic environments.
- Endosymbionts are species that live inside the cells of other creatures and have a symbiotic connection with them. Ancient endosymbionts include mitochondria and chloroplasts.
- Meiosis is a kind of cell division that creates four gamete cells, each containing half of the chromosomes of the parent cell. Reproductive sexuality is essential.
- Phylogenetics is the study of evolutionary history and relationships among species.
- Taxonomy is the study of species categorization.
Questions
1. Which of these features are found in all protists?
- Microscopic size
- Sexual reproduction
- Well-defined nucleus
- Autotrophy
2. Why is the giant kelp not considered a plant?
- Present in the ocean
- Too large
- Does not support other living organisms
- Does not have tissue-level organization of cells
3. Earliest classification of protists included bacteria and fungi.
- True
- False
Answers
- C is correct.All protists have a well defined nucleus. Not all are microscopic. Some form large colonies, stretching to tens of meters. Some reproduce sexually, while others reproduce by creating genetic clones. Protists can be autotrophs or heterotrophs. Some are even pathogenic.
- D is correct.Kelps are large colonies of functionally independent cells. They do not have tissue-level organization of cells, unlike plants.
- True.Protists were initially thought to be the primitive versions of plants and animals and included all microscopic organisms.
