Micro Exam 3 L5

15. Be able to describe an overview of the life cycle of green algae?

a. In this species, the mature cells (1) are haploid and contain a single cup-shaped chloroplast. In response to environmental stress, cells develop gametes (2). Gametes of different mating types (+ or -) fuse to form diploid zygotes (3), which contain a durable coat to survive harsh conditions. After dormancy, meiosis (4) results in 4 haploid individuals (2 + / 2 -) which mature. Some mature cells will reproduce asexually (5) which involves resorption of flagella and two rounds of mitosis to form immature haploid cells called zoospores (6) which also mature.

4. Where are each of the 5 types of algae discussed found regarding depth. Why are some algae species (red algae and brown algae) found at deeper depths.

1. 1. Green algae, cyanobacteria, diatoms, and dinoflagellates are found on or near the surface. 2. 2. Brown algae is typically found at slightly deeper depths. 3. 3. Red algae is found at the deepest depths where light can still penetrate.

2. What are algae? What types of organisms are considered algae? What are some common characteristics of algae?

photoautotrophs which lack roots and stems of plants. Algae may be unicellular or multicellular. Some scientists include cyanobacteria as algae. Algae can be found in several eukaryotic supergroups (though most are in Archaeplastida and the SAR clade). 1. Most have cellulose walls 2. Are photoautotrophs and carry out oxygenic photosynthesis using chlorophyll (in chloroplasts) 3. Require high moisture (mostly aquatic) 4. Most reproduce both sexually and asexually 5. Do not infect humans, though some produce toxins

1. What are the 5 supergroups that comprise eukaryotic life? Are most eukaryotes unicellular or multicellular?

Archaeapastida, SAR, Excavata, Amoebozoa, Opisthokonta. Unicellular

6. What is phytoplankton? In addition to diatoms, what other two major groups of organisms are also key components of phytoplankton?

7. Many diatoms are phytoplankton (autotrophic plankton along with cyanobacteria and dinoflagellates) and are the major part of the primary producers of most aquatic food webs. Some also produce toxins.

17. What are some ecological and industrial benefits and consequences of algal life?

Algae have a huge ecological impact and provide many key benefits to humans including the following: • • produce 80% of O2 on earth today • • foundation of many food chains (fix CO2 into glucose) • • petroleum deposits (oils from dead diatoms compressed in the earth) • • diatomaceous earth (diatom silica shells): used for pool filters and metal polishing • • algin and agar used as thickeners

11. What is the supergroup archaeplastida? What are the 3 main groups of algae found in this supergroup? What is unique about the chloroplasts of glaucophytes?

Archaeplastida is a supergroup that includes red algae, green algae, and some land plants. These organisms are classified based on the nature of the plastid used and all are evolutionarily linked to cyanobacteria via plastid production, hence their name. • Glaucophytes: small group of unicellular freshwater algae which contain chloroplasts called cyanelles that have peptidoglycan. • Green Algae: green algae, many of which are unicellular and multicellular and and take on the green color of their chlorophyll • Red Algae: usually multicellular and include multicellular seaweeds; reddish color comes from phycoerythrin which masks the color of the chlorophyll

3. Know the key similarities and differences between brown algae, red algae, green algae, diatoms, and dinoflagellates. The key information for these organisms can be found in the table in the powerpoint in class.

There are at least 10 distinct phyla containing algae species and 3 of them contain multicellular organisms. However, the most commonly described clades of algae are brown algae (phaeophyta), red algae (rhodophyta), green algae (chlorophyta), diatoms, and dinoflagellates. Shown below in the table are their key structural and functional similarities and differences.

10. What is alternation of generations? What is the difference between heteromorphic and isomorphic generations? What are sporophytes, gametophytes, and zoospores?

a. A variety of life cycles have evolved among multicellular algae. The most complex life cycles often include an alternation of generations, which involves alternating between multicellular haploid and diploid forms. Heteromorphic generations are structurally different, while isomorphic generations look similar. b. Cells on the blades of diploid sporophytes develop into sporangia which produce zoospores by meiosis. Though structurally alike, the zoospores develop into haploid male or female gametophytes. The gametophytes form short branched filaments which grow on subtidal rocks. The male gametophytes produce sperm and the female gametophytes produce eggs. Upon fertilization, they produce a new sporophyte.

9. What are brown algae? What pigments do they contain? What is the name of the main body of a brown alga? Be able to identify and/or describe the following structures: thallus, holdfast, tipe, blades, air bladders.

a. Brown algae (Phaeophytes) are the largest and most complex algae. They are multicellular and mostly marine. Most contain pigments called xanthophylls such as fucoxanthin, which gives them their brownish appearance. b. The main body of a brown algae is called the thallus and consists of a root-like structure called the holdfast, a stem-like structure called the stipe, and leaf-like structures called blades. Many often have air bladders or floats to keep them upright in water. c. Many brown algae species are often eaten and used for a variety of industrial applications.

14. What are the two main phylogenetic groups of green algae? What are the main characteristics of charophytes and chlorophytes? What characteristics of charophytes that they share with plants?

a. Charophytes: a division of fresh water algae which share many properties with land plants including the following: (1) rings of cellulose-synthesizing proteins, (2) peroxisomes, (3) flagellated sperm, and (4) phragmoplasts (a mitotic structure) b. Chlorophytes: a division of mostly fresh water algae (with some marine and terrestrial species known). Most are unicellular, however larger size and greater complexity emerged with chlorophytes due to the use of one or more of the following unique adaptations: c. 1. Formation of colonies 2. Formation of true, multicellular bodies 3. Repeated divisions of nuclei without cell divisions

5. What are diatoms? What unique structure do they exhibit and of what two substances is it made? What is bilateral symmetry?

a. Diatoms are microscopic, unicellular or filamentous algae with complex cell walls called frustules that consist of pectin (a polysaccharide) and a layer of silica (SiO2). They can have a wide range of cellular structures and store their energy generated through photosynthesis as an oil. b. More than 200 genera and an estimated 100,000 species of diatoms are believed to exist. Most diatoms exhibit bilateral symmetry (a line of symmetry along a central axis of the organism)

7. What are dinoflagellates? What substance reinforces their cell walls? What is meant to be mixotrophic? What is phagotrophy?

a. Dinoflagellates are microscopic, unicellular algae which are all plankton (free-floating organisms). They exhibit characteristic cell walls reinforced by cellulose plates. Most dinoflagellates live in the ocean, though some freshwater species are also known. b. Dinoflagellates are phytoplankton and also are often endosymbionts with marine animals including coral reefs. A few forms are also known to be parasitic. Many dinoflagellates are mixotrophic, combining photosynthesis with ingestion of prey (phagotrophy).

13. What are green algae? What characteristics do they exhibit?

a. Green algae have cellulose cell walls, contain chlorophyll a and b, and store starch. Most scientists believe that green algae gave rise to modern terrestrial plants. Most species of green algae are microscopic, although unicellular and multicellular species do exist. b. Green algae are divided into two main phylogenetic groups: 1. Charophytes 2. Chlorophytes

8. What are algae blooms and which type of algae are generally associated? Why are they potentially toxic? What is Karenia brevis and why is it important? What toxin does K. brevis produce?

a. Occasionally, explosive population growths occur with dinoflagellates resulting in blooms. Due to carotenoids in dinoflagellate plastids, these blooms are often brownish red, pink, or bright red in appearance. b. These "red tides" are often associated with high toxicity due to release of neurotoxins from the dinoflagellates expanding within them. Karenia brevis is a key dinoflagellate found in the Gulf of Mexico and is responsible for "red tides" in the region and secretion of brevetoxin. c. The toxins produced by these organisms result in high mortality in invertebrates and fish who consume them. Human ingestion of molluscs that have fed on these blooms can lead to human toxicity and even death.

12. What are plastids? How did algae get their plastids? What is secondary endosymbiosis?

a. Plastids are double-membrane organelles found in plants, algae, and some other eukaryotes. Plastids are the sites of manufacturing and storage of key chemical compounds in the cell. Most plastids contain pigments and like mitochondria, they are likely derived from endosymbiosis of a cyanobacterium or other photosynthetic bacteria into a eukaryotic cell (primary endosymbiosis) giving rise to red and green algae. b. Secondary endosymbiosis c. events where algae became engulfed likely resulted in the development of other photosynthetic organisms such as dinoflagellates and euglenoids.

16. What are red algae? What pigment gives it its color? What characteristics do red algae exhibit?

a. Red algae are mostly multicellular, reddish to near black in color, photoautotrophs which are found primarily in marine systems. Red algae get their pigmentation from phycoerythrin, a pigment which is accessory to chlorophyll. Several notable seaweeds are red algae including "Nori" (Porphyra). Their life cycles are quite diverse and may include alternation of generations, however unlike other algae, their sperm are unflagellated and thus require water currents for fertilization.