Please highlight all the terms in blue. Make sure to study these notes…there will be a quiz over these notes on Monday/Tuesday, January 21st & 22nd. When you are done with the notes: Read and study the chapter in the textbook. Read and review your notes. Come prepared for discussion and activities in class.

Chapter 30: Protists

Introduction Domain Eukarya is the third domain on the tree of life. Eukaryotes range from single-celled organisms the size of bacteria to sequoia trees and blue whales. Eukaryotes are diverse, yet share fundamental features that distinguish them from bacteria and archaea: Most are large, have more organelles and a more extensive cytoskeleton A nuclear envelope Multicellularity evolved multiple times Asexual and sexual reproduction

Protists Introduction All eukaryotes except land plants, fungi, and animals. Tend to live in environments where they are surrounded by water most of the time.

Open ocean: Surface waters teem with microscopic protists, Figure 27.1 Open ocean: Surface waters teem with microscopic protists, such as these diatoms. Shallow coastal waters: Gigantic protists, such as these kelp, form underwater forests. Intertidal habitats: Protists such as these brown algae are particularly abundant in tidal habitats. Figure 27.1 Protists Are Particularly Abundant in Aquatic Environments. 1 mm © 2017 Pearson Education, Inc.

Why Do Biologists Study Protists? Biologists study protists because they have: Impacts on human health and welfare Ecological importance Critical to understanding evolution of plants, fungi, and animals

Impacts on Human Health and Welfare Several types of protists can cause human disease, and some also cause disease in our crops. Irish potato famine of 1845: caused by the protist Phytophthora infestans Type of water mold Led to emigration, and mass starvation caused deaths

Malaria is one of the world’s most chronic public health problems Caused by five species of the parasitic protist Plasmodium and is transferred to humans from mosquitoes. The cell types that make up each stage of the Plasmodium’s life cycle are each specialized for infecting a specific host cell.

Figure 27.2 Haploid (n) Plasmodium cell type present in mosquito saliva that infects humans MITOSIS MITOSIS Diploid (2n) Mosquito bite (n) (n) Infection of liver cells in human Human host Mosquito host Infec tion o f gut w all in m o Male gametes (n) Figure 27.2 Plasmodium Lives in Mosquitoes and in Humans, Where It Causes Malaria. squito Plasmodium cell types present in human blood that infect mosquitoes MEIOSIS followed by MITOSIS Mosquito bite Zygote FERTILIZATION (2n) Female gamete (n) © 2017 Pearson Education, Inc.

Table 27.1 Some Human Health Problems Caused by Protists. © 2017 Pearson Education, Inc.

Protists Play a Key Role in Aquatic Food Chains Protists represent just 10% of the named eukaryotic species, but they are extraordinarily abundant. Primary producers—species that produce chemical energy by photosynthesis Production by marine protists represents almost half of the total carbon dioxide that is fixed on Earth. Plankton—diatoms and other small organisms that drift in the open oceans or lakes

Protists Play a Key Role in Aquatic Food Chains A food chain describes nutritional relationships among organisms. Many of the species at the base of food chains in aquatic environments are protists.

How Do Protists Obtain Food? Bacteria and archaea obtain their food in a wide variety of ways. One of the most important stories in the diversification of protists was the evolution of novel methods for finding food. Many protists ingest their food—they eat bacteria, archaea, or other protists whole, this process is called phagocytosis.

How Do Protists Obtain Food? Protists feed in various ways: Ingesting packets of food Absorbing organic molecules directly from the environment Performing photosynthesis

Ingestive Feeding Ingestive lifestyles are based on eating live or dead organisms or on scavenging loose bits of organic debris. Some protists are large enough to surround and ingest bacteria and archaea. Some protists are large enough to ingest other protists or microscopic animals.

Ingestive Feeding Feeding by phagocytosis is possible in protists that lack a cell wall A flexible membrane and dynamic cytoskeleton allow them to surround and “swallow” prey with pseudopodia (long, fingerlike projections) Many ingestive feeders actively hunt prey and other ingestive feeders attach themselves to a surface. These protists feed by sweeping food particles into their mouth with cilia.

(a) Pseudopodia engulf food. Figure 27.13 (a) Pseudopodia engulf food. Protist Prey 1 µm Pseudopodium (b) Ciliary currents sweep food into gullet. Cilia Figure 27.13 Ingestive Feeding. Food items Gullet 50 µm © 2017 Pearson Education, Inc.

Absorptive Feeding Absorptive feeding—nutrients taken up across plasma membrane, directly from the environment. Some absorptive feeders are decomposers, feeding on dead organic matter, or detritus. Many absorptive feeders live inside other organisms If an absorptive species damages its host, it is called a parasite.

Photosynthesis Autotrophic protists: Produce organic compounds via photosynthesis Range in size from single-cell organisms to giant seaweeds Use carbon dioxide as primary source of carbon

How Do Protists Move? Many protists actively move to find food or light Amoeboid motion is a sliding movement observed in some protists that is accomplished by streaming of pseudopodia Requires ATP Related to muscle movement in animals Key immune system cells in humans use amoeboid motion

Amoeboid motion via pseudopodia Chaos carolinensis Figure 27.14 Amoeboid motion via pseudopodia Chaos carolinensis Figure 27.14 Amoeboid Motion Is Possible in Species That Lack Cell Walls. 0.2 mm © 2017 Pearson Education, Inc.

How Do Protists Move? The other major mode of locomotion involves swimming via flagella or cilia. Flagella and cilia have identical structures, however: Flagella are long and are usually found alone or in pairs Cilia are short and numerous Even closely related protists can use radically different forms of locomotion.

(a) Swimming via flagella (b) Swimming via cilia Figure 27.15 (a) Swimming via flagella (b) Swimming via cilia Figure 27.15 Many Protists Swim Using Flagella or Cilia. © 2017 Pearson Education, Inc.

How Do Protists Reproduce? Asexual reproduction Is based on mitosis and cell division in eukaryotic organisms. Fission in bacteria and archaea Results in daughter cells that are genetically identical to the parent.

How Do Protists Reproduce? Sexual reproduction Is based on meiosis and fusion of gametes Results in daughter cells that are genetically different from their parents and from each other

Life Cycles—Alternation of Generations Alternation of generations— one phase of life cycle based on a haploid form and another based on a diploid form Gametophyte—multicellular haploid form Specialized cells produce gametes (single haploid cells) by mitosis and cell division Two gametes fuse to produce a diploid zygote

Life Cycles—Alternation of Generations Sporophyte—multicellular diploid form Specialized cells that produce haploid cells (spores) via meiosis Spores: are single haploid cells that divide mitotically to form haploid gametophyte

Please highlight all the terms in blue. Make sure to study these notes…there will be a quiz over these notes on Monday/Tuesday, January 21st & 22nd. When you are done with the notes: Read and study the chapter in the textbook. Read and review your notes. Come prepared for discussion and activities in class.