Introduction to Botany. Lecture 14

Alexey Shipunov

Minot State University

September 30, 2015

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 1 / 17 Outline

1 Questions and answers

2 Life cycle Basics Diversity of life cycles Evolution of life cycles

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 2 / 17 Outline

1 Questions and answers

2 Life cycle Basics Diversity of life cycles Evolution of life cycles

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 2 / 17 Questions and answers Previous final question: the answer

In the beginning of mitosis, cell has 10 ng of DNA. How much DNA has each of daughter cells in the end of mitosis?

5 ng

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 3 / 17 Life cycle Basics

Life cycle Basics

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 4 / 17 n − Zygote Cells = gametes n + 2n n Y!

Vegetative Sexual reproduction reproduction

n

2n R! Asexual reproduction

n n

Life cycle Basics Simple life cycle: unicellular organism

Associated terms: mitosis, meiosis (R!), syngamy (Y!), reproduction, sexual reproduction, asexual reproduction, vegetative reproduction, isogamy, heterogamy, oogamy, zygote, gamete, male, female, spermatozoon, oocyte Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 5 / 17 Life cycle Basics Simple life cycle: unicellular organism

n − Zygote Cells = gametes n + 2n n Y!

Vegetative Sexual reproduction reproduction

n

2n R! Asexual reproduction

n n

Associated terms: mitosis, meiosis (R!), syngamy (Y!), reproduction, sexual reproduction, asexual reproduction, vegetative reproduction, isogamy, heterogamy, oogamy, zygote, gamete, male, female, spermatozoon, oocyte Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 5 / 17 Life cycle Basics Multicellularity, or Origin of Death

Sometimes, cells do not part after mitosis. These simple cell aggregates may benefit from their size (e.g., harder to swallow) and putative division of labor (e.g., capture light from different sides and share products of photosynthesis) Next step is to separate germ cells and somatic cells. Somatic cells with eventually die whereas germ cells may give an offspring. This is the beginning of multicellularity. Life cycles of multicellular organisms are based on interleaving gaplont and diplont, the second is making spores

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 6 / 17 Vegetative Sexual reproduction reproduction: (fragments or mitospores) M

n Syngamy n (isogamy type) Gamete mother cell Gametangium n n + Y! – n Gametes

General (sporic) life cycle life cycle

Haplont Diplont 2n Gametic (human) Vegetative reproduction Zygote n (fragments or Asexual mitospores) Spore reproduction:

Meiosis Spore mother cell 2n n R! 2n Spores n Sporangium Zygotic life cycle

Life cycle Basics General life cycle: multicellular organism

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 7 / 17 Life cycle Basics General life cycle: multicellular organism

Vegetative Sexual reproduction reproduction: (fragments or mitospores) M

n Syngamy n (isogamy type) Gamete mother cell Gametangium n n + Y! – n Gametes

General (sporic) life cycle life cycle

Haplont Diplont 2n Gametic (human) Vegetative reproduction Zygote n (fragments or Asexual mitospores) Spore reproduction:

Meiosis Spore mother cell 2n n R! 2n Spores n Sporangium Zygotic life cycle

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 7 / 17 Life cycle Diversity of life cycles

Life cycle Diversity of life cycles

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 8 / 17 Life cycle Diversity of life cycles Sporic life cycle: plants

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 9 / 17 Life cycle Diversity of life cycles Gametic life cycle: animals

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 10 / 17 Life cycle Diversity of life cycles Zygotic life cycle: protists

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 11 / 17 Life cycle Diversity of life cycles Life cycle math

Sexual reproduction ni / / 2n1 O Syngamy (Y!) O

.  . 2n O 2

2 1  . n2 . O

 Meiosis (R!)  n1 o o 2nk Asexual reproduction

1 — zygotic cycle (Y!→R!); 2 — gametic cycle (R!→Y!).

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 12 / 17 Life cycle Evolution of life cycles

Life cycle Evolution of life cycles

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 13 / 17 Life cycle Evolution of life cycles Diplonts grow, haplonts reduce

n Y! zygotic

2n

R!

zygote starts Y! Y! n to grow n 2n Y!

2n 2n

R! n R! R!

2n

sporic Y!

gametic n

R!

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 14 / 17 Life cycle Evolution of life cycles Why diplonts are better?

They have two variants of each gene!

1 Dominance: if one gene is deadly mutated, there is the second working variant 2 Protein production: two genes will give more protein 3 Diversity: if one gene is producing protein adapted to +5...+30◦C and other—to +10...+35◦C, the organism may live under +5...+35◦C

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 15 / 17 Life cycle Evolution of life cycles Summary

Zygotic life cycle has no diplont, gametic life cycle has no haplont, sporic life cycle has both haplont and diplont The evolution of life cycles goes from zygotic to sporic and then to gametic because “diplonts are better”

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 16 / 17 Life cycle Evolution of life cycles For Further Reading

A. Shipunov. Introduction to Botany [Electronic resource]. 2015. Mode of access: http://ashipunov.info/shipunov/school/biol_154

Shipunov (MSU) Introduction to Botany. Lecture 14 September 30, 2015 17 / 17