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similarity in appearance of two groups due to independent evolutionary change. This similarity may be due to either a) convergent evolution (analogous traits) in two organisms b) an evolutionary reversal (a loss of a advanced trait and thus the organism reverts back to using a primitive trait). Ex: frogs with teeth
This has nothing to do with homology; these traits are similar for some reason other than inheritance from a common ancestor
lack a membrane-bound nucleus and membrane bound organelles.
have smaller, simpler genomes than eukaryotes. the DNA is concentrated in the nucleoid region. The single prokaryotic chromosome is a double-stranded DNA molecule in the form of a ring. reproduce only asexually via a process called binary fission. population increase can be rapid
Many of these organisms are referred to as amoebas.
1) The Foraminiferans are planktonic organisms, with thin rays of pseudopods extending through small pores in their shells.
2) The Radiolarians have a internal skeleton made of silica, with fine pseudopods extending from the central cell body supported by a series of microtubules covered by a fine layer of cytoplasm and cell membrane.
- small (0.1 to 10 microns)
- DNA with nonhistone protein, simple circular DNA molecule, DNA not within a nuclear envelope, plasmids present
- binary fission, no mitosis
- they can exchange genes via plasmids
- no mitochondria or chloroplasts, metabolism in cytoplasm
- no ‘9 pairs plus 2’ pattern of microtubules, cell wall composed of disaccharide polymers linked to peptide chains
-large (10 to 100 microns)
-DNA in several chromosomes, more genes than in bacteria, histone and nonhistone proteins, DNA within the nuclear envelope, no plasmids
-mitochondria and chloroplasts, metabolism occurs in these organelles and in the cytoplasm
-cytoplasmic streaming, phagocytosis, cytoskeleton
-‘9 pairs + 2’ pattern, cell wall if present does not have disaccharide polymers linked to peptides
flagella or cilia
-These flagella are structurally and functionally different from bacterial flagella. There is a 9+2 arrangement of microtubules.
-Cilia are shorter, more numerous, have a distinct power stroke and recovery stroke.
Eukaryotic flagella are usually less numerous
used by the amoebae; usually have a front or leading end (pseudopod forms, thickening of ectoplasm into a gel-like (‘gel’) state that contains no organelles, and the more soluble (‘sol’) endoplasm flows towards this cap (which is anchored).
ATP energy is used for this transformation between sol and gel states. Somewhere else in the cytoplasm, sol is converted into gel (endoplasm into ectoplasm) to provide the ectoplasm needed at the leading end
Many are symbionts that inhabit the body fluids, tissues, or cells of hosts.
Different types consume bacteria, other protists, detritus (dead organic matter) and can be parasites on many other organisms.
These symbiotic relationships span the continuum from mutualism to commensalism to parasitism.
-holozoic ( = phagotrophs); they consume whole organisms
-saprozoic ( = osmotrophs), feeding on food in fluid form.
-Many protists form food vacuoles by phagocytosis -The cytoproct is literally a cell anus, where waste vacuoles attach and materials are expelled by exocytosis
most protists are aerobic and possess mitochondria.
Some protists are anaerobic and live in anaerobic environments or have mutualistic bacteria that respire for them.
Some protists are photosynthetic.
Some protists are thought to be fairly ancient; they possess no mitochondria
-produce ammonia as their metabolic waste, which comes from the breakdown of proteins and amino acids; the ammonia is excreted to the outside via diffusion.
-Many protists live in freshwater (hypotonic environments) thus water diffuses in by osmosis constantly.
-marine protists, they live in hypertonic environment, water diffuses out constantly' their cytoplasm is osmotically similar to the seawater.
-syngamy (the union of two gametes)
sometimes protists form small gametes that fuse together to restore the diploid condition.
If the gametes are all alike and the same size, this is called isogamy (isogametes), but in some cases, they are of two different sizes of gametes form (anisogamy, with anisogametes)
a sexual process that occurs in ciliates.
a) Two ciliates of different mating strains meet and fuse along oral grooves.
b) The macronucleus usually disintegrates.
c) The micronucleus undergoes meiosis, producing four haploid micronuclei. Three haploid micronuclei typically disintegrate
d) The fourth haploid micronucleus then undergoes mitosis, forming the male and female pronuclei.
e) The two joined ciliates exchange their male pronuclei, and in each organism, the male and female pronuclei fuse to form a new diploid micronucleus.
f) The two joined cells then separate. Each cell subsequently undergoes mitosis three times and cytokinesis twice, thus each original cell forms four daughter cells with two micronuclei each. In each daughter cell, one micronucleus usually undergoes mitosis many times to produce macronucleus in each daughter cell, the other micronucleus remains as a micronucleus. The advantage of conjugation is that it increases genetic variability.
The only diploid cell is the zygote itself. The zygote forms from the fusion of two haploid gametes (produced by two haploid individuals by mitosis). The zygote undergoes meiosis, creating haploid spores. These spores then undergo mitosis to develop into a haploid multicellular ‘adult’ organism.
1) water scarcity
2) support: water provides some support against the force of gravity (but air does not)
3) increased exposure to the harmful effects of UV radiation (water absorbs UV light).
a) how cellulose fibers are made (cellulose synthesizing complexes)
b) the presence of peroxisomes
c) flagellated sperm cells that resembles the sperm of some charophytes
d) certain details of cell division are common only to land plants and the most complex charophyte algae
e) form and function of chloroplasts
f) the presence of plasmodesmata (observed in some charophytes)
Land plants produce many unique molecules collectively called ____________.
Various _________provide some protection against the harmful mutagenic UV radiation from the sun.
Various _________ have bitter tastes, strong odors, or toxic effects that help defend land plants against herbivorous animals or microbial attack.
The mosses (most common), liverworts and hornworts; nontracheophytes (they do not possess tracheids, a type of conducting cell found in the vascular plants.
Not considered a monophyletic group.
Most live on land, although a few have reinvaded freshwater; there are no marine ______.
Probably were the first to evolve adaptations for life on land. For the most part lack vascular tissues that transport water and nutrients throughout the body. The gametophyte is the dominant generation in the life cycles of bryophytes.
ferns and their relatives. The other major groups of land plants evolved vascular tissue and are known as the vascular plants. Vascular tissues (xylem and phloem) are composed of cells joined into tubes that transport water and nutrients throughout the plant body. these are sometimes called seedless plants, because there is no seed stage in their life cycles.
In vascular plants, the branched sporophyte is dominant and is independent of the parent gametophyte
A sporophyte-dominant life cycle evolved in ______________
From the earliest known vascular plants to the modern vascular plants, the sporophyte generation is the larger and more complex multicellular plant body type. The leafy fern plants that you are familiar with are sporophytes
produces two kinds of spores.
A few ferns (the water ferns) are heterosporous. Both homosporous and heterosporous sporophytes have sporangia, in which diploid cells undergo meiosis to produce the spores.
a) Megaspores develop into female gametophytes. b) Microspores develop into male gametophytes
The great majority of modern-day plant species are the flowering plants
Flowering plants evolved in the early Cretaceous period about 130 million years ago.
1) the reduction of the gametophyte
2) the evolution of the seed
3) the evolution of pollen
All seed plants are _________, with two different sporangia.
a) Megasporangia have megaspore mother cells that produce megaspores, which give rise to female (egg-containing) gametophytes.
b) Microsporangia have microspore mother cells that produce microspores, which give rise to male (sperm-containing) gametophytes
_____ eliminated the liquid-water requirement for fertilization.
1) The microspores, released from the microsporangium, develop into ______ grains.
2) wind or animals carry ____ until pollination occurs, when they land near the ovule.
3) A ____ grain will elongate a fertilization tube into the ovule and deliver one or two sperm into the female gametophyte.
The evolution of ____ in seed plants led to even greater success and diversity of plants on land.
help disperse the seeds of angiosperms.
a) A fruit is a mature ovary. As seeds develop from ovules after fertilization, the wall of the ovary thickens to form the fruit. Fruits protect dormant seeds and aid in their dispersal.
b) functions like a kite or propeller, enhancing wind dispersal.
c) Many angiosperms use animals to carry seeds.
composed of one carpel (or several carpels fused together). The carpels are the central, innermost ring of sporophylls that produce megaspores and their products, female gametophytes.
a) The sticky stigma is at the tip of the carpel, the stigma receives pollen.
b) The style leads to the ovary at the base of the carpel.
c) The ovary protects the ovules and seeds
A microspore divides once by mitosis and produces a generative cell and a tube cell.
a) The generative cell will eventually form sperm. b) The tube cell, enclosing the generative cell, produces the pollen tube, which delivers sperm to the egg.
c) The entire structure is the _________, an immature male gametophyte.
d) A pollen grain becomes a mature gametophyte when the generative cell divides by mitosis to form two sperm cells.
Both sperm fuse with nuclei in the embryo sac.
a) One sperm fertilizes the egg to form the zygote. b) The other sperm combines with the two polar nuclei to form a triploid nucleus in the central cell. This large cell will give rise to the __________, a food-storing tissue of the seed.
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