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

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 giverise 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

Phagocytosisof an aerobicbacterium

Heterotrophiceukaryote

Photoautotrophic eukaryote

Phagocytosisof cyano-bacterium

c.f. Archezoa

c.f. Forams

Features of ‘Protists’

• All eukaryotes

• Mostly unicellular

• ‘Primitive’ and thought to have diverged early from a ‘universal ancestor’

• Very diverse

Types of ‘Protist’

Euglenozoa Alveolata Rhodophyta Plantae

GreenAlgae

RedAlgae

Dinoflagellates

Ciliates

Apicomplexans(sporozoans)

Euglenoids

Kinetoplastids

Stramenopila = Diatoms+Golden Algae+Brown algae+Water moulds

Archezoae.g Giardia

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.

Summary of evolutionary relations

Archezoa

Euglenozoa

Stramenopila

Green algae

Plants

Fungi

Animals

time

Distance apart

Alveolates

Red algae

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

– euglenoidsPhotosynthetic but may beheterotrophic or mixotrophic

– KinetoplastidsSymbiotic 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

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