EBIO- Summative Assessment #2

Why is it problematic to have a kingdom Protista?

Kingdom protists have organisms whose features resemble plants, animals and fungi so this kingdom does not have a well-defined boundary and it forms a link with plants, animals, and fungi. It is a heterogenous kingdom. Therefore, it is difficult for biologists to agree on a classification of protists.

What is the sister taxa (i.e., the group of species most closely related to) of green plants?

Red algae is most closely related. The sister taxa of land plants is charophytes (green algae).

What is a seed?

Seed refers to the fertilized, matured ovule that contains an embryonic plant, stored material and a protective coat or coats. A seed is a mature ovule that comprises an embryo or a miniature undeveloped plant and food reserves, all enclosed within a protective seed coat.

Where did the first eukaryotic cells come from???

The endosymbiotic theory posits that some eukaryotic cell organelles, such as mitochondria and plastids, evolved from free-living prokaryotes. Scientists think that protists are the oldest eukaryotes, Protists most likely evolved from prokaryotic cells, as explained by the endosymbiotic theory.

Describe the major characteristics of angiosperms

Like gymnosperms, angiosperms are seed-producing plants. They are distinguished from gymnosperms by characteristics including flowers, endosperm within their seeds, and the production of fruits that contain the seeds.

What are some pieces of evidence that support the endosymbiotic origin for these organelles?

Many striking similarities between prokaryotes and mitochondria; membranes, mitochondria have their own cell membranes, just like a prokaryotic cell does. DNA- each mitochondrion has its own circular DNA genome, like a bacteria's genome, but much smaller.

Can you explain where the mitochondria in all eukaryotic cells came from?

Mitochondria and chloroplasts likely evolved from engulfed prokaryotes that once lived as independent organisms. At some point, a eukaryotic cell engulfed an aerobic prokaryote, which then formed an endosymbiotic relationship with the host eukaryote, gradually developing into a mitochondria.

What characteristics are useful for defining an organism as protist?

- Eukaryotes. -Unicellular -Free-living -Motile -Aquatic -Microscopic -Asexual reprpoduction

Uni-cellular vs multi-cellular

A colony of single-cell organisms is known as colonial organisms. The difference between a multicellular organism and a colonial organism is that the individual organisms that form a colony or biofilm can, if separated, survive on their own, while cells from a multicellular organism (e.g., liver cells) cannot.

What is a protist?

A protist is any eukaryotic organism that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor, the exclusion of other eukaryotes means that protists do not form a natural group, or clade.

Different types of seed dispersal

Because plants cannot walk around and take their seeds to other places, they have developed other methods to disperse (move) their seeds. The most common methods are wind, water, animals, explosion and fire.

In which ways are Bryophytes and ferns similar? In which ways are they different?

Both groups are primitive plants. The key difference between bryophytes and ferns is the presence and absence of vascular tissues. Bryophytes do not have vascular tissue. Hence they are non-vascular plants while ferns have a vascular tissue hence they are vascular plants.

Describe some evolutionary novelties developed by Bryophytes and by ferns that made them better adapted to terrestrial life than green algae.

Bryophytes and ferns developed cuticle and stomata.

What are some basic resources land plants need in order to survive? How do green algae access these resources? How do land plants do?

CO2 Sunlight Nutrients and minerals (soil) Water

For any photosynthetic eukaryote that you see today, can you explain where the chloroplasts came from?

Chloroplast evolutionarily derives from a primitive cyanobacteria that was engulfed by non-photosynthetic cells and, progressively, after losing most of its DNA, became the actual chloroplast that retains only a fraction of the cyanobacterial genes.

Describe at least 3 challenges that the first land plants would have faced during colonization of land.

Drying out Lack of support No roots for nutrients How to distribute nutrients

What are some ecological roles of fungi? How have humans exploited fungi for their benefit?

Ecological roles of fungi: Some fungi are decomposers which mean that they break down plant and animal debris, thus cycling nutrients and increasing their availability in the soil. They can also propel nitrogen fixation and phosphorus mobilization, two of the main nutrients required for plant development and productivity. Humans use fungi for many purposes, including as food or in the preparation of food. Humans also use fungi for pest control. In addition, fungi can be used to produce citric acid, antibiotics, and human hormones. Fungi are model research organisms as well.

What is the propagule of fungus?

Endomycorrhizal fungal propagule - are the structures of endomycorrhizal fungi that are capable of forming a symbiotic association with plant roots. These structures are endomycorrhizal spores and root fragments colonized by endomycorrhizal fungi.

What is the endosymbiotic theory, what is some supporting pieces of evidence for the theory, and how does it apply to the origin of certain eukaryotic organelles?

Endosymbiosis is an evolutionary theory which posits that eukaryotic cells arose from prokaryotic cells. The theory further articulates that the mitochondria found in today's eukaryotes evolved from aerobic bacteria and that the chloroplasts found in today's plant cells arose from cyanobacteria

How have humans used protists for their benefit?

Protists are used to make medicines to treat high blood pressure, digestion problems, ulcers, and arthritis. They are also used as food additives. Some protists can even decompose and recycle nutrients used by human beings.

What are some ecological roles of protists?

Protists function at several levels of the ecological food web: as primary producers, as direct food sources, and as decomposers. In addition, many protists are parasites of plants and animals that can cause deadly human diseases or destroy valuable crops.

What characteristics distinguish protists from groups of organisms?

Protists have nuclear membranes around their DNA. They also have other membrane-bound organelle. Many protists live in aquatic habitats, and most are motile,

What do protists do out in the real world, and do you have any interactions (directly or indirectly) with protists on a daily basis?

Protists make up a huge part of the food chain and supply much of the oxygen we breathe. Protists are used in medicine and as food additives.

Discuss the four major highlights in the evolutionary history of plants

The first step was the development of mosses, followed by vascular plants ferns The next evolutionary step that took place was the development of cone-bearing plants (gymnosperms), and finally, flowering pants (angiosperms)

Life cycle of fungi

The life cycle of fungi can follow many different patterns. For most of the molds indoors, fungi are considered to go through a four-stage life cycle: spore, germ, hypha, mature mycelium. Can reproduce sexually or asexually

How is the life cycle of seed plants different from the life cycle of non-seed plants? What is the evolutionary significance of those differences?

The major difference between the life cycle of seedless and seed plants is that the seedless plants produce spores, and the seed plants produce seeds for propagation.

what are some differentiating characteristics between prokaryotic and eukaryotic cells?

The primary distinction between these two types of organisms is that eukaryotic cells have a membrane-bound nucleus and prokaryotic cells do not.

what other novel evolutionary adaptation emerged among the protists that was not present among the prokaryotes?

The protists have evolved from prokaryotes during which the nucleus divided via mitosis, histones were associated with the DNA, an endomembrane system and a cytoskeleton were formed, and they developed the ability to make flagella or cilia for movement from one place to another.

What major innovations enable gymnosperms to transition fully to life on land?

The small haploid (1n) cells are encased in a protective coat that prevents dissociation (drying out) and mechanical damage. Pollen grains can travel far from their original sporophyte, spreading the plant's genes and can reach the female organs without dependence on water.

What is the difference between unicellular and multicellular life?

Unicellular organisms are made up of only one cell that carries out all of the functions needed by the organism, while multicellular organisms use many different cells to function. Unicellular organisms include bacteria, protists, and yeast.

What is the sister taxa (i.e., the group of species most closely related to) of land plants?

Zygnematales, the conjugating green algae (zygnematales) are now suggested to be the extant sister group to land plants, providing the novel understanding for character evolution and early multicellular innovations in land plants.

Describe the different structures of plants.

Plants have a root system, a stem or trunk, branches, leaves, and reproductive structures (sometimes flowers, sometimes cones or spores, and so on).

What is pollen?

Pollen is a powdery substance produced by seed plants.

Hapltonic Life cycle

A type of life cycle with a dominant haploid stage. Hapltonic is a kind of life cycle where the zygote takes the lead, meaning, zygotes are the only diploid cell. It divides itself mitotically in order to give rise to a brand new plant.

What characteristics are shared by all cells?

All cells share four common components. 1) A plasma membrane, an outer covering that separates the cell's interior from its surrounding environment 2) cytoplasm, consisting of a jelly-like region within the cell in which other cellular components are found. 3) DNA, the genetic material of the cell; and 4) ribosomes, particles that synthesize proteins.

List at least 4 differences between the diplontic human life cycle and the haplodiplontic life cycle of land plants below:

Alternation of generations (between haploid and diploid) Have spores Mitosis forms gametes Multicellular haploid stage

What are some useful characteristics that can differentiate groups/species of protists from each other? [Note: you can consider any type of cell covering (absence/presence, size, shape, color, composition), mechanism for movement, method of feeding, method of reproducing, among others...]

Animal-like protists are heterotrophs and have the ability to move. Plant-like protists are autotrophs that photosynthesize Fungi-like protists are heterotrophs, they have cells with cell walls and reproduce by forming spores

What are some basic characteristics of land plants, e.g., in terms of mode of nutrition (autotrophic? heterotrophic?), number and types of cells (uni- or multicellular? prokaryotes or eukaryotes?), and mode of reproduction (sexual? asexual? both?)?

Autotrophic Multicellular Eukaryotic Both sexual and asexual reproduction

What is a fungus? Consider an answer from both a morphological/structural and metabolic perspective.

Fungi can be single celled or very complex multicellular organisms. They are found in just about any habitat but most live on the land, mainly in soil or on plant material rather than in sea or fresh water. A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. Fungi can be divided into basic morphological forms, yeasts and hyphae. Fungi contain a remarkable range of metabolic pathways, sometimes encoded by gene clusters, enabling them to digest most organic matter and synthesize an array of potent small molecules.

Structure of fungi

Fungi consist of long thread-like structures known as hyphae. These hyphae together form a mesh-like structure called mycelium. Fungi possess a cell wall which is made up of chitin and polysaccharides.

Which characteristics do Bryophytes and ferns share with their algal ancestors?

Have flagellated sperm that needs water to move

Did plants first evolve on water or on land?

Plants evolved from living in water to habiting land because of genes they took up from bacteria, according to a new study which establishes how the first step of large organisms colonizing the land took place

What are some basic differences between prokaryotic and eukaryotic cells?

No prokaryotic cell has a nucleus; every eukaryotic cell has a nucleus. Prokaryotic cells have no mitochondria; nearly every eukaryotic cell has mitochondria. Prokaryotic cells have no organelles enclosed in plasma membranes; every eukaryotic cell has a nucleus and organelles, each enclosed in plasma membranes.