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SEXUAL AND ASEXUAL REPRODUCTION Evangeline D. Pascual Institute of Biological Sciences, UPLB
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SEXUAL AND ASEXUAL REPRODUCTIONEvangeline D. PascualInstitute of Biological Sciences, UPLB
Objectives
1. Differentiate sexual from asexual reproduction in terms of i. number of individuals involvedii. similarities of offspring to parents
2. Describe the process of fertilization
Sexual Reproduction
Offspring inherits genetic material from two parents (1/2 from each)
Three sexual life cycles
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Animal Plants & some algae Fungi & some protists
The Human Life Cycle
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
fertilization restores diploid
condition- combining two haploid sets of chromosomes
Reproductive System• automatic classification • which set of sex organs we have
Male Reproductive System
Female Reproductive System
Sex Determination
FERTILIZATION
- when egg and sperm meet a. external
- female sheds eggs -male fertilizes eggs in the
environment- moist habitats
-sea urchins, fish, amphibians
Fertilization
b. internal- sperm deposited in/nearby
female reproductive tract- thousands of sperms surround egg
but only one can enter
10 hrs 18 cm 48 hours hundreds, only one
(Picture: "From Conception to Birth" by Alexander Tsiaras and Barry Werth)
Sperm cells
• http://londonstimestshirts.files.wordpress.com/
• a. First trimester• - fertilization • - division of zygote • - blastocyst implantation • - placenta• - organogenesis
• - heartbeat by four weeks!
Human Pregnancy
Fertilization and implantation
Pregnancy test
www.natlstar.com
Sexual Reproduction in Plants
Development of a male gametophyte(in pollen grain)
(a)
Microsporangium(pollen sac)
Microsporocyte
Microspores (4)
Each of 4microspores
Generative cell(will form 2 sperm)
(LM)75 m
20 m
MEIOSIS
MITOSISMale gametophyte(in pollen grain)
Nucleus of tube cell
Ragweed pollen grain(colorized SEM)
Key to labels
Haploid (n)Diploid (2n)
(b) Development of a female gametophyte (embryo sac)
100
m
MEIOSIS
MITOSIS
Key to labels
Haploid (n)Diploid (2n) (LM)
Embryo sac
Ovule
Megasporangium
Megasporocyte
IntegumentsMicropyle
Survivingmegaspore
Antipodal cells (3)
Polar nuclei (2)
Egg (1)
Synergids (2)
Ovule
Integuments
Female gam
etophyte(em
bryo sac)
http://mac122.icu.ac.jp/gen-ed/higher-plants-etc-gifs/10fl-plant-life-cycle.JPG
b. Plant Reproduction
• http://www.fs.fed.us/wildflowers/pollinators/whatispollination.shtml
• http://www.washingtonch.k12.oh.us
botanistinthekitchen.wordpress.com
Asexual Reproduction
like begets like
- offspring whose genes all come from one parent
- without fusion of egg and sperm
Asexual Reproduction
- relies entirely on mitosis single individual – sole parent
offspring - genome = exact copy of parent's
http://search.dilbert.com/
Asexual Reproduction Invertebrates
1. Fission – parent divides approximately in half
ex. sea anemone
Sea anemone
Longitudinal fission involves a complete lengthwise split creating 2 individuals
http://creationwiki.org/Image:Anemone129181039_689f0201bf.jpg
Asexual Reproduction
2. Budding – new individuals split off from existing ones
ex. Hydra (relative of jellyfish)
- bud: localized mass of mitotically dividing cells
Asexual Reproduction
3. Fragmentation and regeneration
– breaking of the body into several pieces
- develop into adults ex. sponges
Asexual Reproduction Advantages:
- animals that live in isolation produce
offspring without locating mates
- many offspring in a short amount of
time
Asexual Reproduction
Plants1.Vegetative reproduction
- modified stems - runner, rhizome, corm, tuber, bulb
Ginger rhizome
http://en.wikipedia.org/ wiki/File:Gingembre.jpg
taro
Taro corms Colocasia esculenta
http://en.wikipedia.org/wiki/Colocasia_esculenta
• http://waynesword.palomar.edu/
Asexual Reproduction
horizontal stem- runner : aboveground
- rhizome : underground
Asexual Reproduction
- Tuber : enlarged tip of slender rhizome
short underground stem
- Bulb : with overlapping fleshy scales
- Corm : with less or no scales
Tuber
Bulb
CormRhizome
Runner
gladiolus
• www.e-bloomin.com urbanext.illinois.edu
www.bryophyllum.com
Asexual Reproduction
2. Parthenogenesis - embryo without nuclear/cellular
fusion or from tissue surrounding embryo sac
Asexual Reproduction
3. Vegetative propagation
cuttings
grafts
leaves
www.pinterest.com
Artificial Vegetative Propagation• Cutting- use of plant to reproduce (Ex. )
• Layering- stem is over and covered with will root and form plant (Ex. )
• Grafting- stem or bud of one plant is to another plant
(Ex. )
partSpider plant
bent soilnew raspberry
joined
Seedless fruit treepermanently
Modes of Reproduction4.Tissue culture
propagation- new plant induced
to arise from cell/tissue
- orchid, rice, corn, wheat
Summary
Sexual Reproduction
• Two parents• Offspring are a
combination of both parents and are therefore different from each parent• Variation/diversity
Asexual Reproduction
• Single parent• Offsprings are identical to
parents
