Know the evidence that supports the “endosymbiotic theory of the origin of eukaryotic organelles” described in Jeff Ihara’s lecture. How do we know that these organelles derived from bacteria?
- Mitochondria, and chloroplast.
- They have their own DNA
- Through binary fission, they replicate DNA on its own schedule
What is the “ozone layer?” When did it originate? How did it originate? What did it allow to happen as far as plants are concerned?
- Ozone is produced naturally in the stratosphere when highly energetic solar radiation strikes molecules of oxygen, O2, and cause the two oxygen atoms to split apart in a process called photolysis.
- One billion years ago, early aquatic organisms called blue-green algae began using energy from the Sun to split molecules of H2O and CO2 and recombine them into organic compounds and molecular oxygen (O2). This solar energy conversion process is known as photosynthesis.
- It allowed organisms to come onto the land by protecting them from the intense UV light of the sun.
What is a “self-replicating molecule”? Why was RNA thought to be the molecule from which life originated?
- construction of an identical copy of itself. Cell division. During cell division, DNA is replicated and can be transmitted to offspring during reproduction.
- RNA catalyzes its own replication and catalyze the chemical reaction of primitive cells. It was able to catalyze its own replication without the help of DNA. RNA was the first molecule of heredity, so it evolved all the essential methods for storing and expressing genetic information before DNA came onto the scene.
What is the role of auxin in the development of a plant?
If one side of a plant is away from the light, does that side have higher or lower auxin production?
What causes a plant to bend toward the light? What is the consequence of cutting off the apical meristem in a growing bush?
- The role of auxin in the development of a plant is to stimulate elongation. Promotes the formation of lateral and adventitious roots, regulate the development of fruits, enhance apical dominance, promote vascular differentiation.
- The cells on the plant that are farthest from the light have a chemical called auxin that reacts when phototropism occurs. Therefore, if one side of the plant is away from the light, that side of the plant have higher auxin.
- The high concentration of auxin on the shady side causes the plant cells on that side to grow more so it bends toward the light, because light is the energy source for plant growth, plants have evolved highly sensitive mechanisms for perceiving light.
- The consequence of cutting off the apical meristem in a growing bush is a reduction in the amount of auxin the growing bush receives. Therefore, it may affect the plant’s growth.
What is the relationship between microsporophylls, megasporophylls, homospory, and heterospory?
The relationship between them is that most seedless plants are homospory, meaning that they only produce one kind of spore, which give rise to a bisexual gametophyte. Ferns and other close relatives of seed plants are homosporous, which suggests that seed plants had homosporous ancestors. At some point, seed plants or their ancestors became heterosporous.
microsporophylls (4) vs megasporophylls (4)
microsporophylls
- modified into stamens
- sheds it spores
- spores develop into male gametophytes
- male gametophyte formed near female gametophyte
megasporophylls
- rolled to produce a carpel in angiosperms
- does not shed its spores
- spores develop female gametophytes
- female gametophyte is formed inside the megasporangium
How does a bacterial flagellum work?
How does it work differently in a spirochaete?
- bacteria have a single, tail-like flagellum or a small cluster of flagella, which rotate in coordinated fashion, much like a propeller on a boat engine, to push the organism forward.
- Spirochetes are corkscrew-shaped bacteria. It has a flagellum that resides inside the cell within the periplasmic space. Allowing them to enter and adapt to the host environment, and penetrate through matrices that usually inhibit the motility of most other bacteria.
What are the benefits for a bacterium to be motile? (2)
- The benefit is that it can disperse more rapidly and potentially finding new food resources more rapidly than non-motile.
- Move away from repellant and move towards attractants more rapidly.
What are the major adaptations that plants evolved in order to move from water to land? (5)
How were they able to persist for long time periods without water? (3)
How did they persist in the presence of insect herbivores?
1st question
- Waxy cuticle: covers the outer surface of the plant, prevents evaporation, and protects against radiation damage from UV light.
- Stomata: are pores or holes which allow for exchange of gasses between the plant cells and the environment.
- Roots: anchor plants to the soil and, and serve as conduits for water absorption.
- Mycorrhizal fungi: are associated with approximately 80% of all land plant species, provide additional surface area for absorption of both water and nutrients from the soil.
- The alternations of the genetic life cycle, which includes both a multicellular haploid and multicellular diploid stage
2nd question
- desiccation tolerance: many mosses can dry out to a brown and brittle mat, but as soon as rain or a flood makes water available, mosses will absorb it and are restored to their healthy green appearance.
- colonize environments where droughts are uncommon. Ferns, which are considered an early lineage of plants, thrive in damp and cool places such as the understory of temperate forests.
- plants moved away from moist or aquatic environments and developed resistance to desiccation, rather than tolerance.
3rd Question
Evolved to have spines, thorns, and toxic chemicals.
What is pollen?
Powdery substance comprising pollen grains which are male macro-gametophyte of seed plants, which produce male gametes (sperm cells).
What methods can you use to promote rooting of cut shoots?
Dip it in auxin analog. Unlike the inhibitory effect that auxin had on shoot branching, auxin increases the rate of side-root formation, from the various types of lateral meristem and pericycle tissues.
What is the sequence in the evolution of plastids among plants? (3)
- Organelles called plastids, are the main sites of photosynthesis in eukaryotic cells. They included Chloroplasts and other pigment cytoplasmic organelles that enables the harvesting and conversion of light and CO2 into food and energy.
- Plastids may derive from cyanobacteria engulfed via endosymbiosis by early eukaryotes, giving cells the ability to conduct photosynthesis
- The proposed ancestors of plastids were photosynthetic bacteria.
What happened in the Paleozoic that was important to the evolution of life? (5)
- the Cambrian explosion occurred (Origin of life)
- Cambrian explosion included the evolution of arthropods and chordates
- extraordinary diversification of marine animals
- most of the major groups of animals first appear in the fossil record
- driven by oxygen, and oxygenic photosynthesis
Double fertilization
Double fertilization is a mechanism of fertilization in angiosperms in which two sperm cells unite with two cells in the female gametophyte (embryo sac) to form the zygote and endosperm (triploid).
How does Toxoplasma alter its host behavior and why does it do this?
It alters the personalities of infected individuals by increasing risk-taking behaviors. Infection usually does not manifest in acute symptoms in human adults, and this is termed latent chronic infection. It is in those with weakened immune systems (babies and sick people) where infection can result in severe symptoms or even death.
What are the characteristics of a Stramenopile? (3)
All 3 groups of stramenopiles (diatoms, golden algae, and brown algae) have a distinct flagellum, which has numerous fine, hairlike projections. In most stramenopiles, this “hairy” flagellum is paired with a shorter “smooth” (non-hairy) flagellum.
Diatom
- unicellular algae
- glass-like wall made of silicon dioxide embedded in an organic matrix
- live diatoms can withstand pressures as great as 1.4 million kg/m2
- highly diverse group of protists
- among the most abundant photosynthetic organisms both in the ocean and in lakes
- they are so widespread and abundant that their photosynthesis activity affects global CO2 levels
Golden algae
- have yellow and brown carotenoids, cells are flagellated (both flagella attached near one end of the cell)
- most are unicellular but some are colonial
- components of freshwater and marine plankton
- photosynthetic but some are mixotrophic (can absorb dissolved organic compounds or ingest food particles including living cells)
Brown algae
- all are multicellular and most are marine
- common temperate coasts that have cold water currents
- they are brown because of the carotenoids in their plastids
- have specialized structures that resemble organs in plants
- lack true tissue and organs
- have adaptations that enable their main photosynthetic surfaces to be near the water surface
- some of them are used in soups, and salad dressing
If you know the phylogenetic relationship of three taxa, what do you know about these taxa?
Which have the greatest similarity?
Which are most dissimilar?
- They have a common ancestor. - The ones that have the same more recent ancestor have the greatest similarity.
- The one that is on it’s own and is connected to the original common ancestor is the most dissimilar from the others
How does water and nutrients move in a xylem near the roots and near the leaves?
Are the water/minerals under positive or negative pressure?
- Water is passively transported into the roots and then into the xylem. The forces of cohesion and adhesion cause the water molecules to form a column in the xylem. Water moves from the xylem into the mesophyll cells, evaporates from their surfaces and leaves the plant by diffusion through the stomata.
- They are under negative pressure.
How do sugars get transported in the phloem? (4)
- formed by the plant during photosynthesis
- carried throughout the parts of the plant by the vascular system
- Phloem, the vascular tissue responsible for transporting organic nutrients around the plant body, carries dissolved sugars from the leaves or storage sites to other parts of the plant that require nutrients.
- Within the phloem, sugars travel from areas of high osmotic concentration and high water pressure, called sources, to regions of low osmotic concentration and low water pressure, called sinks.
How does water get into a plant, as opposed to simply passing through?
Water enters the plant via the roots. Water enters the root by osmosis and moves along through the root cells in the same way until it gets to the xylem vessels. These vessels carry water up the stem to the leaf. Water is lost from the leaves of plants by evaporation.
What is a meristem and where on a plant do you find meristems responsible for primary growth of a shoot, root, secondary growth of a shoot, root, lateral branching of the shoot, root? (5)
- the tissue in most plants containing undifferentiated cells (meristematic cells)
- found in zones of the plant where growth can take place.
- Meristematic cells give rise to various organs of a plant and are responsible for growth
- Primary growth is controlled by root apical meristems or shoot apical meristems
- secondary growth is controlled by the two lateral meristems, called the vascular cambium and the cork cambium.
What are Hemiptera? Why were they mentioned in lecture? (3)
- a large order of insects (as the true bugs) that have mouthparts adapted to piercing and sucking and usually two pairs of wings
- undergo an incomplete metamorphosis
- include many important pests.
What are Chlamydia and what is unique of different about that group? (5)
- a genus of pathogenic bacteria that are obligate intracellular parasites
- The bacterium is Gram-negative
- lacks peptidoglycan in its cell wall
- has a small needle-like projection called a type III secretion apparatus
- serves as a conduit form the bacteria to the cytoplasm of the host cell
