BIO 112 Exam 2

Protists

Protists

Characteristics: Most are Unicellular but some are multicellular eukaryotic organisms that are in several kingdoms, they live in a diversity of habitats, but most are aquatic. Discovered 1.8 billion years ago.

Evolution of Protist

• Protistan diversity has its origins in endosymbiosis​

• Endosymbiosis is a relationship between two species in which one organism lives inside the cell or cells of the other organism (the host).

• Divides all eukaryotes (including protists) into four supergroups​

Plastid Evolution

• The evolution of mitochondria gave rise to the eukaryotes

• Plastids arose later when a heterotrophic eukaryote engulfed a photosynthetic cyanobacterium ​

• Two lineages of photosynthetic protists, red and green algae, evolved from the plastid-bearing ancestor

Endosymbiosis

• This theory states that an early ancestor of eukaryotic cells (a host cell) engulfed an oxygen-using nonphotosynthetic prokaryotic cell.

• Eventually, the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont (a cell living within another cell). Over the course of evolution, the host cell and its endosymbiont merged into a single organism, a eukaryotic cell with the endosymbiont having become a mitochondrion.

• At least one of these cells may have then taken up a photosynthetic prokaryote, becoming the ancestor of eukaryotic cells that contain chloroplasts.

**Trypanosoma

• A protist under the Excavata supergroup, specifically they are euglenozoans.

• Trypanosoma brucei causes "sleeping sickness," with its vector (carrier) being the Tsetse fly, and effects sub-saharan africa. This is fatal if left untreated (there is medication).

• Trypanosoma cruzi causes "chagas disease," with its vector (carrier) being the triatomine insect, "kissing bug;" blood sucking. The parasite is transmitted through their feces (after they feed/bite they leave behind feces). There is medication for this disease that kills the parasite. This effects mostly mexico, South and Central America, and some in the U.S.

**Plasmodium

• A protist under the SAR supergroup, specifically apart of the Aveolates.

• At least 4 species cause the disease malaria, Vivax is the name of one.

• Transferred through the Anopheles Mosquito.

**Dinoflagellates Characteristics

• Protists under the SAR supergroup, specifically apart of the Aveolates.

• They are unicellular, have 2 flagella, and are made of cellulose plates (rigid).

• Evolved from secondary endosymbiosis of red algae.

• Diverse in nutritional modes (photoautotrophs, heterotrophs, and mixotrophs). Most live in marine and freshwater.

**Dinoflagellates (Beneficial and detrimental)

• Beneficial: Many are primary producers, photosynthesizes and photoautotrophs. Many dinoflagellates are symbionts with corals.

• Detrimental: Causes "red tides," (aka harmful algal blooms (HABs)). This means there is too much replication of the dinoflgaellates in the water. Some species produce toxins that can harm and kill fish, as well as irritate human skin, not good to breathe them in either. They also get into seafood (can make humans very sick if eaten).

• Species known to cause red tide are Karenia brevis and Pfisteria.

Diatoms

• These are protists under the SAR supergroup, specifically they are Stramenopiles.

• They are unicellular algae that are photoautotroughs, with a very strong cell wall that contains hydrated silica that makes them look glass-like.

• There ecological role is primary producers of Oxygen, they produce 20-25% of the global oxygen. They live in oceans and lakes (phytoplankton).

• They have many economic purposes like being in toothpaste, pool filters, cleansers, etc.

Foraminiferans

• Aka "Foram." A protist under the SAR supergroup, specifically apart of the rhizarians.

• Forams are found in both the ocean and fresh water. Most species live in sand or attach themselves to rocks or algae, but some live as plankton.

• Foram fossils are excellent markers for correlating the ages of sedimentary rocks in different parts of the world.

Radiolarians

• A protist under the SAR supergroup, specifically apart of the rhizarians.

• These are mostly marine and have delicate, intricately symmetrical internal skeletons that are generally made of silica.

**Upwelling mechanism

• The upward movement of deep cold water ​

• Supports the growth of plankton and seaweed

• Phytoplankton communities rely on upwelling of cold, nutrient-rich water from the below

• Warm surface water acts as a barrier to upwelling​

**Upwelling effects

• Results in waters that contain more nutrients and lower temperatures.

• Supports the growth of plankton and seaweed

• Phytoplankton communities rely on upwelling of cold, nutrient-rich water from the below

Paleobtoany

• The study of ancient plants (basically plant fossils)

Paleobtoany colonization of land by plants and prehistoic landscape

• Land surface was largely lifeless for much of Earth's history.

• Prokaryotes lived on land 3.2 billion years ago.

• Within the last 500 million years, small plants, fungi, and animals joined them ashore.

• The first forests appeared around 385 million years ago.

• Over 325,000 known plant species exist today.

• Plants supply oxygen and serve as a key source of food for terrestrial animals.

• Plants physically create habitats required by other organisms.

Paleobtoany anatomical features (that help conserve water)

• Cuticle

  • Any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, which provide protection

  • Conist of wax and other polymers

• Stomata

  • A microscopic pore surrounded by guard cells in the epidermis of leaves and stems that allows gas exchange between the environment and the interior of the plant

• Apical Meristems

  •  Localized regions of cell division at the tips of roots and shoots, aiding elongation.

Paleobtoany (Factors needed for colonization)

• Many species of charophyte algae inhabit shallow waters and can survive occasional drying.

• Natural selection favors algae that can survive when not submerged.

• A layer of a durable polymer called 

  • Sporopollenin: A durable polymer that covers exposed zygotes of charophyte algae and forms the walls of plant sores, preventing them from drying out

• Bright sunlight, abundant carbon dioxide, and nutrient-rich soil near water's edge favored plant colonization 

• Being so far from water developed new challenges plants had to overcome like lack of water and gravity 

Alternation of generation

• A key traits appears in nearly all plants but is absent in the charophytes

• Type of plant life cycle consisting of multicellular forms that gives rise to each other in turn.

• The multicellular haploid gametophyte produces haploid gametes (sperm and eggs) by mitosis

• The multicellular diploid sporophyte produces haploid spores by meiosis

• Spores develop into gametophytes and fertilized eggs (zygotes) develop into sporophytes

Gametophyte

• Haploid cell, needs a lot of water to reproduce

• bryophytes are gametophyte dominant in their life cycles

Sporophyte

• Diploid cell (2 sets of chromosomes), spore-producing, does not dry out

• pteridophytes, gymnosperms, and angiosperms are all sporophyte dominant in their life cycles.

Gametophyte and sporophyte (Which organisms have which phase as the dominatn phenotype)

• Bryophytes (nonvascular plants: mosses, liverworts, and hornworts) are Gametophyte Dominant

• Gymnosperms (vascular, cones, naked seeds, pollen) and Angiosperms (vascular, flowering plants, seeds covered by fruit, pollen) are Sporophyte Dominant

Antheridia and Archegonia

• Archegonia, female gametangia, produce a single nonmotile egg.

  • Female = MEGA

• Antheridia, male gametangia, produce many motile sperm.

  • Male = MICRO

Antheridia

Haploid structure or organ that produces and contains male gametes

Archegonia

Haploid structure or organ that produces and contains female gametes

Anther

male

Arche

Female

**Gymnosperms Characteristics

• Vascular, Heterospory (bisexual gametophyte produces both male and female spores), naked seeds (no fruit covering), pollen (contains male gametophyte)

• sporophyte is the dominant stage of the lifecycle.

**Gymnosperms reproduction

• Gymnosperms reproduce through the production of cones. There are two types of cones: male cones (microstrobili) and female cones (megastrobili).

  • most gymnosperms have strobili, clumps of sporophylls in cone-like structures

• Male cones produce pollen, which contains the male gametophyte. Pollen is released and carried by wind or insects to reach the female cones.

• Female cones contain ovules, which house the female gametophyte. The pollen lands on the receptive surface of the cone and fertilizes the ovules.

• Fertilization leads to the formation of seeds within the cone.

**Gymnosperms groups

• form a clade that produce seeds that are not enclosed in chambers ("naked seeds")

Ginkgo

• Ginkgo is a type of gymnosperm. It is a unique tree that is the only living species in its division, Ginkgophyta. Ginkgo trees are native to China and are known for their fan-shaped leaves. Ginkgo trees are able to survive in harsh urban environments.

Cycad

A type of gymnosperms that have large cones and palm-like leaves.

Gnetophyta

• A type of gymnosperms that is divided into three categories: Gnetum, Ephedra, and Welwitschia.

• Some species are tropical, whereas others live in deserts.

• There are trees, shrubs, and vines. Cones and large leaves are common too.

Conifers

A type of gymnosperms, including pines, firs, and redwoods; most are Evergreens. They have woody cones.

Pollen

contains the male gametophyte

**Seeds (Why are seeds important)

• A seed is an embryo packaged with a supply of nutrients inside a protective coat

• Seeds provide evolutionary advantages over spores

  • Seeds are multicellular; spores are single cells

  •  Seeds can remain dormant for years until conditions are favorable for germination, whereas spores are shorter-lived

  • Seeds have stored food to nourish growing seedlings; spores do not provide nourishment to gametophytes 

  • Seeds can be transported longer distances by wind or animals, but spores usually drop closer to the parent plant

• Seedless vascular plants have an extensive vascular transport system, but do not produce seeds

• The majority of living plants are seed plants—vascular plants that produce seeds

Angiosperms (Structure compared to gymnosperms)

• form a clade that produce seeds that develop inside chambers that originate within flowers

• Nearly 90% of living plant species are angiosperms

• Are heterosporous: produce two kinds of spores (same)

• Angiosperms megasporangia usually have two integuments (different)

  • Integument: layer of sporophyte tissue that contributes to the structure of an ovule of a seed plant

**Xylem, Phloem (different type and where they occur)

• Both are Vascular Tissue: transports materials in stems, roots, and leaves.

• Xylem carries water and minerals up from up from roots, and they are tube shaped DEAD cells. Only moves upward.

• There are TWO types of Xylem: Vessel elements (THICKER tubes of xylem), and Tracheids (THINNER tubes of xylem). Both are water conducting. Their walls provide a system of microscopic water pipes. Food moves up and down the plant.

• Phloem carries nutrients throughout the plant (sugars, amino acids, etc) and they are tubed shaped LIVING cells. These living cells are empty of many of the organelles, so there is a companion cell that provides some of the things it needs. It is next to the sieve plate, which has pores to faciliate the flow of fluid (sugars and water) between cells.

**Pollen Fertilization of an ovule

• Pollination, which precedes fertilization, is the placing of pollen on the stigma of a carpel.

• After pollination, the pollen tube discharges two sperm into the female gametophyte.

• Two sperm are needed for double fertilization, a process in which one sperm fertilizes the egg, forming a zygote and eventually an embryo, while the other sperm combines with the polar nuclei, giving rise to the food-storing endosperm.