Biodiversity and conservation

 Biodiversity is defined as the totality of genes, species and ecosystems of a given region,

It is the variety and variability of life form (all animals, plants and microbes on earth) and the ecological complexes in which they occur. 

The term was first coined by Walter G. Rosen(1985),however the term was popularized by the American socio-biologist Edward Wilson(1988)

 BIODIVERSITY AND CONSERVATION

·       Biodiversity: the term biodiversity refers to the totality of genes, species, and ecosystems of a region.

·       Types of biodiversity described by Edward Wilson:

o    Genetic diversity: A single species might show high diversity at the genetic level over its distributional range.

§   Medicinal plant Rauwolfia vomitoria of Himalayan range produces active chemical reserpine shows genetic variation.

§   India has more than 50000 different strain of rice.

§   1000 varieties of mango.

·       Species diversity: different species of a single animal like frog.

·       Ecological diversity: diversity in the ecosystem level like desert, rain forest, mangroves, coral reef, wetlands, estuaries etc.

How many species are there on Earth and How many in India?

·       According to IUCN (2004), 1.5 million of plants and animals are in our biosphere.

·       Robert May places global species diversity at about 7 millions.

·       More than 70 percent of all the species recorded are animals.

·       All plants constitute about 22 percent.

·       Among animals insects constitute 70 percent.

·       India has only 2.4 percent of the world’s land area; its share of global species diversity is impressive 8.1 percent.

·       India is considered one of the mega diversity countries of the world.

Pattern of Biodiversity:

Latitudinal gradients:

·       Species diversity decreases as we move away from the equator towards the pole.

·       Tropic (23.5^o N to 23.5^o S) harbors more species than temperate and pole

·       The largely tropical Amazonian rain forest in South America has the greatest biodiversity on earth:

·       40,000 species of plants.

·       3000 species of fishes.

·       1300 of birds.

·       427 amphibians

·       378 reptiles

·       More than 1, 25,000 invertebrates.

Why tropical rain forest has greater biodiversity:

·    Unlike temperate regions subjected to frequent glaciations in the past, tropical latitudes have remained relatively undisturbed for millions of years and thus, had a long evolutionary time for species diversification.

·       Tropical environments. Unlike temperate ones, are less seasonal, relatively more constant and predictable, promotes niche specialization and lead to greater species diversity.

·       There is more solar energy available in the tropics, which contribute to higher productivity.

Species area relationship:

·       ALEXANDER VON HUMBOLDT observed within a region species richness increased with increasing explored area but only up to a limit.

       The relation between species richness and area for a wide variety of taxa turns out to be a rectangular hyperbola.

·       On a logarithmic scale the relationship is a straight line describe by the equation 

    LogS = logC +Z log A    Where S= species richness, A = Area, Z = slope of the line (regression coefficient), C = Y- intercept.

·       It has been noted that regardless of the taxonomic group or region the slope of the regression line are amazingly

   similar. However, for a very large area like the entire continent the slope of  the  line  is steeper.

Importance of species diversity to the Ecosystem:

·       Community with more species generally tends to be more stable than those with less species.

·       A stable community should not show too much variation in productivity from year to year; it must be resistant or resilient to occasional disturbances (natural or man-made)

·       Stable community must be resistant to invasion by alien species.

 David Tillman’s long-term field experiment finds that:

·    Plots with more species showed less year to year variation in biomass

·    Increased diversity contributed to higher productivity.

The rivet popper hypothesis:

·    In an airplane (ecosystem) all parts are joined together by thousands of rivets (species).

·   If every passenger starts popping a rivet to take home (species extinct), it may not affect flight safety initially but as more and more rivets are removed the plane becomes dangerously weak.

·     Further more which rivet is removed may also be critical.

·     Loss of rivets on the wings (key species) is obviously a more serious threat to flight safety than loss of a few rivets on the seats or windows inside the plane.

Loss of Biodiversity:

The IUCN Red List (2004) documents the extinction of 784 species.

·       Recent extinction includes:

·     Dodo (Mauritius).

·     Quake (Africa)

·     Thylacine (Australia)

·     Stiller’s cow (Russia)

·     Three subspecies of tiger (Bali, Java, Caspian).

·       Since the origin and diversification of life on earth there were five episodes of mass extinction of species.

·       The sixth mass Extinctions in progress now.

How the’ sixth Extinction’ is different from the previous five extinctions.

·       The current extinction rate is 100 to 1000 times faster.

·       All others are pre-human period, this one is anthropogenic.

Effect of biodiversity loss:

·       Decline in plant production.

·       Lowered resistance to environmental perturbations such as drought.

·       Increased variability in certain ecosystem processes such as plant productivity, water use, and pest and disease cycle.

Causes of biodiversity loss:

·       The present loss is all due to human activity (anthropogenic)

·       There are four major causes “The Evil Quartet” are as follows:

Habitat loss and fragmentation:

·       Most important cause driving animals and plants to extinct.

·       The tropical rain forest reduced to 6 % from 14 % of earth land surface.

·       The Amazonian rain forest is called as ‘lungs of the planet ‘is being cut cleared for cultivating soya beans.

·       Degradation of many habitat by pollution is also threatens the loss of diversity.

·       Large areas are broken into figments also the cause of diversity loss.

Over-exploitation:

·       When ‘need’ turns to ‘greed’ it leads to over-exploitation of natural resources.

·       Many species extinctions in the last 500 years (Stiller’s cow, passenger pigeons) were due to over- exploitation.

·       Many marine fish populations around the world are over harvested.

Alien species invasion:

·       The alien species became invasive and cause decline or extinction of indigenous species.

·       Nile perch introduced into Lake Victoria in east Africa led to extinction of 200 species of cichlid fish in the lake.

     ·       Parthenium, (carrot grass), Lantana, and water hyacinth (Eichornia) posed a thread to indigenous species.

     ·       African cat fish Clarias gariepinus for aquaculture purposed is posing a threat to indigenous catfishes in our rivers.

Co-extinction·: 

· When a species becomes extinct, the plant and animal species associated with it an obligatory way also become extinct.

·     When a species becomes extinct, the plant and animal species associated with it an obligatory way also become extinct.

 ·      Extinction of Host species leads to extinction of the parasite also.

·       Co-evolved plant-pollinator mutualism where extinction of one invariably lead to the extinction of the other.

BIODIVERSITY CONSERVATION:

Why should we conserve Biodiversity?

 Reason for conservation biodiversity is grouped into three categories.

 a. Narrowly utilitarian.

      b.  Broadly utilitarian

      c.  Ethical

      Narrowly utilitarian:

·       Human derive countless direct economic benefits from nature-

·       Food (cereals, pulses, fruits), firewood, fiber, construction material.

·       Industrial products (tannins, lubricants, dyes, resins, perfumes)

·       Products of medicinal importance.

·       Bioprospecting: exploring molecular genetic and species-level diversity for products of economic importance.

Broadly Utilitarian

·       Amazonian forest along produce 20% of oxygen during photosynthesis.

·       Pollinator layer: bees, bumblebees, birds and bat that pollinate the plant without which seed cannot be produced by plants.

·       Aesthetic pleasure we get from the biodiversity.

How do we conserve biodiversity? In situ conservation:

     ·       When we conserve and protect the whole ecosystem, its biodiversity at all level is protected – we save the entire forest to save the tiger. This approach is called in situ (on site) conservation.

     ·       Biodiversity hot spot: regions with very high levels of species richness and high degree of endemism.(species confined to that region and not found anywhere else)

·       Hot spot in biodiversity is also regions of accelerated habitat loss.

·       Out of 34 hot spot in the world, three hot spot located in India:

         a.  Western Ghats and Srilanka.

         b.  Indo-Burma.

         c.  Himalaya.

·       Other protected area under in situ conservations are:

         a.    18 biosphere reserve-The first Biosphere Reserve in India is the Nilgiri Biosphere Reserve .

         b.  103 national park-A national park is an area set aside by a national government to preserve the natural environment. A national park may be set aside for purposes of public recreation and enjoyment or because of its historical or scientific interest. 

          c.  543 wild life sanctuary-A wildlife sanctuary is an area where animal habitats and their surroundings are protected from any sort of disturbance. The capturing, killing and poaching of animals is strictly prohibited in these regions.

 ·       Sacred groves: tract of forest were set aside, and all the trees and wildlife within were venerated and given total protection.

Ex-situ conservation:

    threatened animals and plants are taken out from their natural habitat and placed in special setting where they can be protected and given special care.

·      Zoological Park.

·       Botanical garden

·       Wildlife safari.

·       Conservation of gamete by cryopreservation.

·       Genetic strains are preserved in seed bank. Convention on Biodiversity:

·       “The earth Summit” held in Rio de Jeneiro in 1992 called upon all nations to take appropriate measures for conservation of biodiversity and sustainable utilization of its benefits.

World Summit on Sustainable development held in 2002 in Johannesburg, South Africa, 190 countries pledged their commitment to achieve by 2010 a significant reduction in the current rate of biodiversity loss at global, regional and local level.

 

Human reproduction

 Chapter-3 HUMAN REPRODUCTION

Events of Human Reproduction

Gametogenesis : formation of gametes.

Insemination : Transfer of sperm in female genital tract.

Fertilization : fusion of sperm and ovum.

Implantation : attachment of blastocyst with uterine wall for further development.

Gestation : Embryonic development

Parturition : Delivery of the baby. 

The Male reproductive system

1. Penis :

a. Urination

b.     Sexual intercourse

c.     Corpus cavernosum- spongy tissue that fills with blood to make penis erect

d.      Glans- the head, end of penis

e.     Foreskin

i.  Covers glans,

ii.  May be removed surgically in an operation

2.  Scrotum   

a.  Located behind penis

b.  Contains two testes

c.  Temperature sensitive (Sperm must be made in cooler conditions i.e, 2-3⁰ C lower than body temperature) 

3. Testes

a.  Sperm is produced by the seminiferous tubules due to FSH

b.  Testosterone is produced by Leydig cells due to LH

Sertoli cells : Provide nutrition to developing germ cells.

Interstitial cells / Leydig cells : Synthesize & secrete testicular hormone called androgens.

ACCESSORY DUCTS :

Epididymis:    Stores sperm until they have matured.

Vas deferens: Tube that leads from the epididymis to the urethra. Many sperm cells are stored here too.  

ACCESSORY GLANDS :

Prostate gland:     Provides an alkaline fluid that can protect sperm from harsh vaginal acids.

Seminal Vesicles:    Produce food for sperm. Food "Fructose"

Cowper's gland:      Produces clear lubricating fluid

SPERM

SEMINIFEROUS TUBULES

Head : It contains a elongated haploid nucleus, covered by acrosome. It filled with hydrolytic enzymes to dissolve the membrane of ovum for fertilization. Neck : It contains two centrioles helps in first cleavage division of zygote. Middle Piece: contains numerous mitochrondria which produce energy for movement of tail that facilitate sperm motility essential for fertilization Tail : helps in Sperm movement

Spermatogonium : it is diploid contains 46 chromosomes.   Primary Spermatocyte (2n): it complete 1st meiotic equal division (reduction) & forms 2 secondary spermatocytes.   Secondary spermatocytes : it is haploid, undergo the 2nd meiotic div to produce four equal haploid spermatids.   Spermatids : They transformed into spermatozoa (sperms) by the process called spermiogenesis with the help of FSH.   Spermiation : After spermiogenesis, sperm heads become embedded in the sertoli cells and finally released from seminiferous tubules by the process of spermiation.

The Female Reproductive System :

Ovary: i) Each ovary contains immature ova (eggs) in follicles. ii)  Females born with lifetime supply of eggs (250,000-400, 000 in each ovary) iii)  Ovaries release ovum -. Almost all ova degenerate between birth and puberty. iv)  Approx. 400 eggs will be ovulated over woman's life. v)  Egg is the largest human cell. vi)  Ovaries are located lower abdomen. 1 left and 1 on the right.   Fallopian tubes i) Two thin tubes attached to the upper sides of uterus ii)  Tubes terminate near the ovaries but are not attached iii) "Fimbriae" are finger-like structures on the end of each tube iv) Tubes conduct egg to uterus by use of small hairs called "cilia" v) Fertilization of ovum takes place in the ampullary- isthmic junction of the fallopian tubes. Egg viable for only 24-48 hours after ovulation.

Uterus: i)Pear-shaped organ located in lower abdomen. ii)Muscles(myometrium) stretch to allow baby to develop. Oxytocin starts labor contractions. iii)Lining of uterus (endometrium) thickens with blood-rich tissue due to progesterone. iv)Endometrium supports embryo/fetus during growth. v) Placenta It is the interface between baby and mother. If not pregnant, lining breaks down and is discharged from body through vagina. This is menstruation (period). vi) Cervix connects uterus to vagina. Like a door that opens during ovulation. Cervical mucous closes the door at all other times.

EXTERNAL GENITALIA:

Vagina (Birth canal) :

  ·   Menstrual blood leaves the body, Organ of intercourse , Muscular stretches to allow a baby to grow

  ·   Vaginal opening partly remains closed by thin membrane of tissue called hymen. May be stretched or torn during any physical activity or first intercourse.

Cervix:

·   Located at inner end of vagina, Opening of uterus into vagina ,

·   Mucous prevents bacteria and viruses from entering uterus, Lets sperm into uterus after ovulation

·   Where baby also passes through during vaginal birth

  Labia: Two (2) layers of skin, which fold over the opening to vagina and urethra

      ii)  Inner labia (labia minora)               iii)Outer labia (labia majora)

·   Pubic hair grows on outer labia

 Clitoris: Small organ, 5 to 10 millimeters long; Located at junction of inner labia near front of body Contains erectile tissue& sexually sensitive.

Mons pubis :Cushion like fatty tissue covered by skin and pubic hair

Gametogenesis & its hormonal regulation : 

FSH and LH from the pituitary:	FUNCTION / PRODUCTION
Hormone	In Females	In Males
FSH Controls à	Eggs + Estrogen (Follicular development)	Spermiogenesis
LH Controls à	Ovulation + Corpus Luteum	Testosterone (Spermatogenesis)

 Differentiate between: Spermatogenesis and Oogenesis :

Spermatogenesis	Oogenesis
Produces male gametes (sperm)	produces female gametes (oocytes)
–occurs in the seminiferous tubules (in testes)	–occurs in the ovaries
–occurs throughout life after puberty	occurs after puberty until menopause
may produce 3,00,00,000 per day	–humans normally produce one oocyte during each ovarian cycle
Primary spermatocyte divide equally to form two similar secondary spermatocytes	Primary otocyte divide unequally to form one large secondary oocyte and a small polar body
One spermatogonium produces 4 functional spermatozoa	An oogonium produces one functional ovum and 3 non functional polar bodies