Botany - Week 7

Evidence for Evolution

1) Species can be modified → selection

2) Comparitive anatomy → homologous structures

3) Fossils → shows simpler forms become more complex

4) Can see hereditary material in cells

Homologous structures

Same organ modified into different structures with different functions

What’s an example of homologous structures in plants?

Leaves can become flower parts, spines, scales, bracts

Analagous structures

Different organs with different origins come to look/function similarly 

Homologous vs analagous structures

Homologous → Same origin, different function

Analagous → Different origin, same function

What type of evolution are homologous structures an example of?

Divergent evolution

What type of evolution are analagous structures an example of?

Convergent evolution

What leads to speciation? 

Reproductive isolation 

Allopatric speciation

Speciation due to geographic isolation

Sympatric speciation

Speciation due only to reproductive isolation

What can lead to reproductive isolation between individuals of the same population?

Mutations or polyploidy

What are the three domains that DNA/RNA evidence divides all organisms into? 

Bacteria, archaea, and eukarya 

Which domains are prokaryotic?

Bacteria and archaea

Which domain is eukaryotic?

Eukarya

Features of prokaryotes

1) Small cell size

2) Simple cell structure

3) No nucleus/membrane bound organelles

4) Absencse of meiosis and sexual reproduction

5) No gamete formation

How do prokaryotic cells divide? 

Asexually by binary fission

Binary fission

Type of asexual reproducton where single parent cell splits into two identical daughter cells

What are the two types of bacteria?

True bacteria and cyanobacteria

True bacteria

1) Most abundant prokaryotes

2) Autotrophic or heterotrophic

3) Non-photosynthetic

Cyanobacteria 

1) Formerly known as “blue-green algae” 

2) Autrophic 

3) Photosynthesis using chlorophyll 

What were the first photosynthetic organisms of Earth?

Cyanobacteria

How did cyanobacteria impact other forms of life?

Released oxygen into atmosphere that allowed for evolution of other life forms

Theory of Endosymbiosis

Suggests that true bacteria and cyanobacteria entered into eukaryotic cells and evolved into mitochondria and chloroplasts

What are the different body forms of cyanobacteria? 

1) Unicellular 

2) Colonial (sheets of cells) 

3) Filamentous (unbranched or branched chains of cells) 

Akinete

Non-photosynthetic cell with thick walls and stores food

What are akinetes used for?

Cyanobacteria produce them to survive unfavorable conditions

What benefits do prokaryotes bring to the world?

1) Natural decomposers

2) Oxygen release

3) Nitrogen fixation

4) Wastewater treatment

5) Probiotics, fermented foods

What are some harmful effects that prokaryotes can have on the world? 

1) Disease 

2) Produce toxins 

3) Make biofilms 

4) Contaminate water bodies 

How can cyanobacterial blooms cause water pollution?

Cyanobacteria form layer (scum/biofilm) on water’s surface → produce toxins that can kill aquatic organisms

Nitrogen fixation

Conversion of nitrogen gas from atmosphere into ammonia and other compounds

What enzyme catalyzes the reaction for nitrogen fixation?

Nitrogenase

Which bacteria perform nitrogen fixation? 

Cyanobacteria and true bacteria 

What specialized cells do cyanobacteria have for nitrogen fixation?

Heterocysts

Where do nitrogen fixing cyanobacteria and true bacteria reside?

Can be free living or in symbiosis with eukaryotes

Rhizobium

True bacterium in legume root nodules

Anabaena 

Cyanobacterium living inside Azolla water fern leaves 

How did eukaryotes evolve a nucleus? 

Thought that plasma membrane folded in → created barrier around chromosomes 

Which domain does the kingdom of protista belong to?

Eukarya

What are some of the simplest organisms in the kingdom protista?

Protozoans, slime molds, algae

Protozoans

Animal-like protists

Slime molds 

Fungi-like protists 

Algae

Plant-like protists

Protozoans, slime molds, and algae all are:

1) Often microscopic

2) Often unicellular

3) Autotrophic or heterotrophic

Algae

Eukaryotes that evolved chloroplasts by developing an endosymbiosis with cyanobacteria and then with other algae

Phases of protist evolution 

1) Prokaryotes (bacteria and archaea) 

2) Early protists → evolved nucleus 

3) Protists with mitochondra (fungi and animals) 

4) Protists with primary plastids 

5) Red algae, green algae, and plants 

How did protists obtain mitochondria?

Endosymbiosis of aerobic bacteria

Plastids 

Family of double-membraned organelles found in cells of plants and algae 

How did protists obtain primary plastids?

Endosymbiosis of photosynthetic cyanobacteria

Where did secondary plastids come from?

Originated where protista enclosed another protista that already had a plastid 

General features of algae

1) Microscopic or macroscopic

2) Unicellular or multicellular

3) Colonial or filamentous

4) Many colors/shapes

5) Mostly autotrophic (photosynthetic)

6) Primary or secondary plastids

What types of algae have secondary plastids?

Euglenoids

Diatoms and brown algae

Dinoflagellates

Characteristics of phylum euglenophyta (euglenoids)

1) More closley related to animals than plants

2) Secondary plastids → green

3) Unicellular

4) Terminal flagellum

5) No cell wall

6) Eyespot → receives light

7) Contractile vacuole → regulates water balance

8) Photosynthetic or heterotrophic

What types of algae exist in the phylum ochrophyta? 

Golden-brown algae (diatoms) and brown algae 

Diatom

Single-celled alga with cell wall of silica

Characteristics of golden-brown algae

1) Diatoms → many shapes/colors/sizes

2) Secondary plastids

3) Unicellular

4) Freshwater and marine

5) Silica in cell wall

6) Golden-brown xanthins often mask chlorophyll

Characteristics of brown algae 

1) Secondary plastids 

2) Multicellular 

3) Mostly marine 

4) Cellulose and algin in cell wall 

5) Brown fucoxanthings often mask chlorophyll 

What type of algae exists in the phylum pyrrophyta?

Dinoflagellates

Characteristics of dinoflagellates

1) Secondary plastids → green

2) Mostly unicellular

3) Moslty marine

4) Mobile → use flagella

5) Most have cell walls

6) Photosynthetic or heterotrophic

What types of algae have primary plastids? 

Red algae and green algae 

What types of algae exist in the phylum rhodophyta?

Red algae

Characteristics of red algae

1) Primary plastids

2) Mostly multicellular

3) Mostly marine, some coralloid

4) Have cell walls

5) Red color phycoerythrin often masks chlorophyll

Coralloid 

Structure resembels coral in shape/appearance