Section 5, Part B Flashcards
4 Kingdoms within Domain Eukarya
Protista, Fungae, Animalia, Plantae
Which of the four kingdom are monophyletic
Animalia, Plantae, and Fungi
Which of the four kingdom are not monophyletic
Protista
What types of organisms are classified as Protists
ex. paramecium - mostly unicellular organisms that don’t fit into other categories
How did multicellularity likely evolve within Domain Eukarya?
Some unicellular eukaryotes form multicellular aggregates that appear to represent an evolutionary transition from single cells to multicellular organisms. Increasing cell specialization then led to the transition from colonial aggregates to truly multicellular organisms. Continuing cell specialization and division of labor among the cells of an organism have led to the complexity and diversity observed in the many types of cells that make up present-day plants and animals, including human beings.
Adaptive advantage of multicellularity
Specialization of function and form
How many times did true multicellularity independently evolve within Domain Eukarya?
Complex multicellular organisms evolved only in six eukaryotic groups: animals, fungi, brown algae, red algae, green algae, and plants.[5] It evolved repeatedly for plants (Chloroplastida), once or twice for animals, once for brown algae, and perhaps several times for fungi, slime molds, and red algae.[6]
Compare sexual and asexual reproduction in eukaryotes
While asexual reproduction only involves one organism, sexual reproduction requires both a male and a female. Some plants and unicellular organisms reproduce asexually. Most mammals and fish use sexual reproduction. Some organisms like corals and komodo dragons can reproduce either sexually or asexually. But in the long term (over several generations), lack of sexual reproduction compromises their ability to adapt to the environment because they do not benefit from the genetic variation introduced by sexual reproduction.
What is the adaptive advantage of sexual reproduction
Meiosis allows for DNA repair
beneficial to produce children who are different from the parents in terms of their genetic makeup as they may be better adapted to the needs of the environment
compare and contrast sexual life cycles in different eukaryotic organisms
a life cycle (or life history) describes the course of development of an organism. A life cycle is the entire history of an organism, usually shown through a series of developmental stages that depicts the changes a species goes through as they pass from the start of a given developmental stage to the inception of the same developmental stage in the next generation.
The key differences between eukaryotic life cycles is the amount of time spent in haploid vs. diploid phases and the meiotic products (spores vs. gametes) that are produced.
The gametic life cycle is the reproductive cycle found in animals and some protistans. The term gametic refers to the fact that gametes are the result of meiosis.
The zygotic life cycle is the simplest sexual life cycle, common among fungi and protists. These organisms are haploid during most of their life cycle.
The sporic life cycle is common algae and plants. The term sporic refers to the fact that spores are the result of meiosis.
Alternation of generations
Alternation of generations (Fig. 3c) refers specifically to a life cycle that includes the alternation between multicellular haploid life stages and multicellular diploid life stages. Diploid forms (sporophytes) produce haploid spores, which divide and develop directly into multicellular haploid structures (gametophytes). Gametophytes then produce haploid gametes, which join with other gametes through fertilization to form diploid sporophytes once again. The diploid and haploid generations alternate, over and over. In some organisms the diploid stage is the dominant form that is responsible for the majority of growth and resource acquisition, whereas in others the haploid stage is dominant.
how many times did alternation of generations independently evolve in eukaryotes and in which lineages
Occurs in Plants, Fungi, and Protists
At least in red algae, brown algae, plants, and others
What role did primary endosymbiosis and secondary endosymbiosis play in the evolution of photosynthetic eukaryotes?
However, a growing body of evidence indicates that the chloroplasts of some algae have not been derived by engulfing cyanobacteria in a primary endosymbiosis like those discussed above, but by engulfing photosynthetic eukaryotes. This is called secondary endosymbiosis. It occurred so long ago that these endosymbionts cannot be cultured away from their host.
In two groups, the eukaryotic nature of the endosymbiont can be seen by its retention of a vestige of a nucleus (called its nucleomorph).
A group of unicellular, motile algae called cryptomonads appear to be the evolutionary outcome of a nonphotosynthetic eukaryotic flagellate (i.e., a protozoan) engulfing a red alga byendocytosis.
Another tiny group of unicellular algae, called chlorarachniophytes, appear to be the outcome of a flagellated protozoan having engulfed a green alga.
The result in both cases: a motile, autotrophic cell containing:
its own nucleus
its own mitochondria
its own endoplasmic reticulum, which contains the endosymbiont with
its own plasma membrane
its own cytoplasm, the periplastid space
its own ribosomes
its own chloroplast, and
its nucleomorph - only a vestige of its original nucleus, but still surrounded by a nuclear envelope perforated with nuclear pore complexes and
containing a tiny but still-functioning genome.
Primary endosymbiosis involves the engulfment of a bacterium by another free living organism. Secondary endosymbiosis occurs when the product of primary endosymbiosis is itself engulfed and retained by another free living eukaryote. Secondary endosymbiosis has occurred several times and has given rise to extremely diverse groups of algae and other eukaryotes.
In which eukaryotic lineages did photsynthesis evolve?
Photosynthetic eukaryotes evolved by ‘endosymbiosis’, in which a eukaryotic ‘host’ cell engulfed a cyanobacterium
from which three ‘primary plastid’ groups evolved: the glaucocystophytes, green algae (or chlorophytes, including the land plants) and red algae (or rhodophytes).
Identify at least one protist group that is convergent with land plants. Explain how the group is convergent.
plant-like green algae and plants
In constrast, the various algae, with the plant-like algae (green algae) and the plants, together constitute a polyphyletic taxon, each apparently independently (red algae, brown algae, green algae) arising from protist ancestors (implying that endosymbiotic chloroplasts are an example of convergent evolution—i.e., arose more than once during evolutionary history).
