BE101 Introduction to Biological Systems Dr. Michael Parkinson

Lecture Structure Lectures in QG15 & QG13 each week. A round up of points and coverage of examination type questions on Monday evening @ 5:00 in QG15 These overheads are available to view as powerpoint presentations at: webpages.dcu.ie/~parkinsm/teaching.htm Any standard Biology text will do for reading around e.g. Mader Biology (all at 570 in the library).

Schedule of topics Evolution of eukaryotes and protists Fungi Plant Evolution Plant reproduction Plant Structure Plant growth and development Photosynthesis

The origins of eukaryotic diversity Dr Michael Parkinson School of Biotechnology The origins of eukaryotic diversity can be traced back approximately 1.8billion years.

What I’m going to cover in this lecture The origin of Eukaryotes The classification of Protists 3 of the more primitive groups of Protists Archezoa Euglenozoa Alveolates

3 things that you should watch for in this lecture The way that eukaryotes have evolved from primitive ancestors The way that the organisms are classified and the factors that affect their classification The ways that protists can affect public health

Evolution of eukaryotes by serial endosymbiosis Nuclear membrane and endoplasmic reticulum formed from invagination of plasma membrane akin to phagocytosis Inclusion of organelles from phagocytosis of aerobic bacterium / cyanobacterium The origin of microtubule structures (flagellae, cilia, cytoskeleton) is unknown

1. Nucleus formation Phagocytosis is a very common phenomenon in Protists. Invagination of the plasma-membrane is expected to give rise to: a double membrane covering around the nucleus, a system of membranes within the cell continuous with the nucleus and the plasma membrane.

2. Origin of organelles c.f. Forams Phagocytosis of cyano- bacterium Photoautotrophic eukaryote Phagocytosis of an aerobic bacterium This scheme fits in very well with what we know about the symbiotic relationships of protists. For example, many members of the Archezoa actively phagocytise aerobic bacteria. Many Foraminifera phagocytise algae, and form long lived symbiotic relationships with them. c.f. Archezoa Heterotrophic eukaryote

Features of ‘Protists’ All eukaryotes Mostly unicellular ‘Primitive’ and thought to have diverged early from a ‘universal ancestor’ Very diverse

Types of ‘Protist’ Archezoa e.g Giardia Euglenozoa Alveolata Rhodophyta Plantae Dinoflagellates Euglenoids Red Algae Green Algae Ciliates Don’t try and take this down. This is just to give you a taste of the different forms of Protists. They are mostly unicellular, and before the electron microscope was invented, it was a nightmare to classify them based on structure. They vary from flagellated (euglenozoa and kinetoplastids) to ciliated (ciliates) to non-motile (apicomplexans), and from single cells (all those mentioned) to quite complex multicellular forms, some very closely related to green plants (brown, red and green algae). Apicomplexans (sporozoans) Kinetoplastids Stramenopila = Diatoms+Golden Algae+Brown algae+Water moulds

Evolutionary relations For many years, all organisms that did not conveniently fit into other groups were placed into the ‘Protists’. Classification is in a very active and dynamic state. Recently, molecular phylogeny based on similarity in DNA + electron microscopy has led to reclassification to give MONOPHYLETIC groups - organisms are grouped if they have a common ancestor.

This is a map of the Eukaryotes based on similarities in the sequence of rRNA. It is too complicated to take down, so just listen and make sense out of it as we go along. The longer the lines are, the more ancient. The Metazoa (animals) and Fungi form fairly tight and distinct groups showing their relatively recent evolution. We see immediately that amonst the rest of the Eukaryotes, the most ancient groups (longest lines) are the Microsporidia, Trichomonads and Diplomonads. These are collectively lumped into the Archezoa, as you’ll see in the next slide. The Euglenophytes and the Amoebae-flagellates are the next most ancient group. These are both normally flagellated. The alveolates form a more recent grouping with ciliates (cilia), dinoflagellates (2 flagellae) and non-motile, parasitic organisms, the sporozoans. If you look at these under the electron microscope, you see small vesicles under the cell surface, Alveolii, hence the name Alveolates. Again a very diverse group is the Stramenopiles. This includes the golden brown algae (single celled), the brown algae (can grow up to 100 feet long), and oomycetes (fungus-like). They all have flagellae at some stage in the life cycle with flimmer (cross hairs). The red algae evolved relatively recently and are closely related to the green algae and plants. The king of the protists (speaking as a botanist) is the green algae and plantae. It is obvious that an amoeboid form of living has evolved independently at least 5 times giving at least 5 different amoeboid groups.

Summary of evolutionary relations Animals Fungi Plants Distance apart Green algae Red algae Stramenopila Alveolates If we were to look at the evolutionary relations of the protists, a picture would emerge pretty much like this. Archezoa are the most ancient (remember the long lines on the chart of 16s RNA evolutionary tree). Euglenozoa Archezoa time

Ways of classifying ‘Protists’ Plantae Archezoa Protista Chromista Plantae Plantae Archezoa Euglenozoa Alveolata Stramenopila Rhodophyta Diplomonads Trichomonads Microsporidians Depending on which textbook you use, you will see the classification of the protists in one of these guises. The one I shall be using is the 3rd one down. I’ll be covering each of these groups in turn. Euglenoids Heterotrophic Flagellates (Kineto-plastids) Dino-flagellates Api-complexans (sporozoans) Ciliates Amoeboids Diatoms Golden Algae Brown algae Water Moulds Red algae Green algae and plants

ARCHEZOA (from Greek Arkhaios meaning ancient) Considered to be the most primitive of all eukaryotes No mitochondria (some engulf bacteria) Mostly parasitic (e.g. Giardia) 3 Sub-groups Diplomonads (includes Giardia) Trichomonads (e.g. Trichomonas) Microsporidians

Giardia An important parasite Transmitted by both water and animals Probably the most important source of holiday diarrhea

Trichomonas An STD

EUGLENOZOA Flagellates 2 sub-groups euglenoids Photosynthetic but may be heterotrophic or mixotrophic Kinetoplastids Symbiotic or parasitic e.g. Trypanosoma, Leishmania

Trypanosoma Causes sleeping sickness in cattle and man in Africa transmitted by the Tsetse Fly In Americas, Chagas disease

Chagas disease / Sleeping Sickness

Life cycle involves biting/sucking insects

Leishmania The life cycles of members of the genus involve a vertebrate host (e.g., the human) and a vector (a sand fly) that transmits the parasite between vertebrate hosts

Cutaneous Leishmaniasis

ALVEOLATA All have small membrane bound cavities (Alveoli) beneath the cell surface. 3 subgroups Ciliates Apicomplexans Dinoflagellates

Ciliates All have cilia for locomotion and feeding Reproduce by binary fission

Trichodina sp. This genus contains many species, perhaps as many as 200, most of which are found as commensals or facultative or obligate parasites on aquatic invertebrates, fish, and amphibians.

Apicomplexans (Sporozoa) All parasites of animals All have a complex at the apex of the cell for penetrating host tissues (Apicomplex) ‘Relict’ plastids possibly related to dinoflagellates with 4 bounding membranes Plasmodium falciparum Pneumocystis carinii (Pneumonia) Toxoplasma gondii (toxoplasmosis) Cryptosporidium parvum (cryptosporidosis)

Apicoplast (plastid of Apicomplexan) 4 membranes Genome of circular plasmid Smallest genome of any plastid (35kb) Codes for a number of genes Provides a means of attacking the parasite

Malaria - Plasmodium/mosquito

Malaria - infection with an Apicomplexan, Plasmodium

Dinoflagellates Abundant components of the phytoplankton Blooms cause red tides in coastal waters Can be an important symbiont in coral reefs