Sexual and asexual reproduction biota ed_pascual

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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

Animal Plants & some algae Fungi & some protists

The Human Life Cycle

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

http://library.med.utah.edu

http://www.biocyclopedia.com

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/

http://www.cabrillo.edu

• 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)

Microsporangium(pollen sac)

Microsporocyte

Microspores (4)

Each of 4microspores

Generative cell(will form 2 sperm)

(LM)75 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)

MEIOSIS

MITOSIS

Key to labels

Haploid (n)Diploid (2n) (LM)

Embryo sac

Megasporangium

Megasporocyte

IntegumentsMicropyle

Survivingmegaspore

Antipodal cells (3)

Polar nuclei (2)

Egg (1)

Synergids (2)

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

• www.ag.auburn.edu

• http://www.esu.edu

botanistinthekitchen.wordpress.com

Asexual Reproduction

like begets like

- offspring whose genes all come from one parent

- without fusion of egg and sperm

- 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

2. Budding – new individuals split off from existing ones

ex. Hydra (relative of jellyfish)

- bud: localized mass of mitotically dividing cells

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

Plants1.Vegetative reproduction

- modified stems - runner, rhizome, corm, tuber, bulb

Ginger rhizome

http://en.wikipedia.org/ wiki/File:Gingembre.jpg

Taro corms Colocasia esculenta

http://en.wikipedia.org/wiki/Colocasia_esculenta

• http://waynesword.palomar.edu/

horizontal stem- runner : aboveground

- rhizome : underground

- Tuber : enlarged tip of slender rhizome

short underground stem

- Bulb : with overlapping fleshy scales

- Corm : with less or no scales

CormRhizome

Runner

gladiolus

• www.e-bloomin.com urbanext.illinois.edu

www.bryophyllum.com

2. Parthenogenesis - embryo without nuclear/cellular

fusion or from tissue surrounding embryo sac

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

• Single parent• Offsprings are identical to

parents