HEREDITY AND EVOLUTION

Homologous organs class x

Examples of Homology

Homology refers to two things that have an equivalent role or relationship. Homology is important in comparative biology since it makes it possible to determine if two different animals or plants share a common ancestor. Essentially, homology in this context means that there are two species that have related parts that do similar things, but that are not exactly the same. 

Homology In the Animal Kingdom

Following are some examples of homology:

·         The arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale are homologous structures. They are different and have a different purpose, but they are similar and share common traits. They are considered homologous structures because they have a similar underlying anatomy. 

·         The forelimbs of a frog, a bird, a rabbit and a lizard look very different because they have evolved differently to account for the specific lifestyles of each animal. However, they share a common ancestor and a common set of bones (the radius, ulna and humerus). The shared bones date back to a prehistoric fish that emerged onto land, eventually becoming an extinct transitional animal from which they evolved. These different structures are also homologous to the arms of people, the wings of the bat, and the other animal parts described above. 

·         The pelvis of a dog, of a cat and of a human and of a snake are homologous structures. 

·         The tailbone of a human being and the tail of a monkey are examples of homology. The tailbone is actually called the tailbone because of this shared lineage. Because a human doesn’t actually have a tail but the tailbone is the last vestige or remains of where a tail would be, it is referred to as “vestigial.” 

·         The leaves of a pitcher plant, a Venus fly trap, a cactus and a poinsettia are all examples of homology. They are homologous structures because, although they have different shapes and different functions today, they all share a common ancestor. 

·         The mouthparts and the antennae of different insects such as the grasshopper, the honeybee, the butterfly and the mosquito are used for different purposes. The grasshopper, for example, primarily bites and chews while the honeybee bites and the butterfly sucks pollen. Although different today, these different parts are examples of homology because they share the same basic structure which was just modified or enlarged as needed for the particular species. 

·         Non-identical chromosomes in DNA that can pair with each other and that are believed to share common ancestry are also examples of homology. They can also indicate that there is a common or shared function in the chromosomes. 

Homologous structures can be traced back to the last common ancestor that the animal’s shared. For example, if the wing of a bat and the forearm of a person are examples of homology, this means that the anatomical structure of the forearm and of the wing were both present in the last common ancestor along the evolutionary chain that was shared by the bird and bat. 

Now you have lots of examples of homology and you have a better understanding of how homology works in the field of comparative biology.  

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Read more at http://examples.yourdictionary.com/examples-of-homology.html#Oa4jyRpXqakC3LoV.99

PROTISTA

• The kingdom includes unicellular eukaryotic organisms.
• They are primarily aquatic
• They have well organized nucleus and complex membranous organelles.
• They have hair like cilia, whip like flagella or pseudopodia for locomotion.
• Some protists are plant like with cellulosic cell wall and chloroplasts. They are autotrophs.Eg: diatoms, dinoflagellates.
• Some protists have animal like cells . They are called protozoans and are heterotrophs or holozoic. Eg: amoeba, paramoecium, Plasmodium

• 

  paramoecium
  

GYMNOSPERMS

GYMNO (NAKED) SPERMA(SEEDS)

• It includes medium sized and tall trees as well as shrubs.Sequoia (giant red wood tree) is one of the tallest tree species.
• Leaves in gymnospems are well adapted to withstand extremes of temperature, humidity and wind. Thick cuticle, sunken stomata and needle like leaves reduce the surface area.
• These are the plants in which ovules are not enclosed by any ovary wall.
• After fertilisation seeds remain exposed and therefore these plants are called naked seeded plants
• Gymnosperms produce microspores and megaspores which are produced in microsporangia and megasporangia borne on sporophylls
• The sporophylls are arranged spirally on axis to form male and female cones respectively.These may be borne on the dsame tree (Pinus) or on different trees( Cycads)



mature female cone pinus

• After fertilisation zygote develops into embryo and ovules develop into seeds.



cycad female cone



cycas male cone

• Gametophyte does not have an independent existence. They remain within the sporangia retained on the sporophyte.



second year male cone pinus

• Children you can watch these videos on youtube for purpose of clarity 

www.youtube.com

Nature Notes Female and Male Pine Cones - Longleaf Pine.

Male or Female Sago, How to tell the difference

 

CHARACTERS OF CRYPTOGAMS

The subkingdom is divided into three divisions.

• Thallophyta
• Bryophyta
• Pteridophyyta

THALLOPHYTA

• This division includes plants that are not differentiated into root, stem, leaf or flower.
• They are aquatic, fresh water as well as marine.
• Vascular tissue is absent.
• sex organs are simple and single celled. Embryo formation after fertilization is absent.
• Life cycle is completed in two phases dominant haploid gametophytic phase and shortlived , diploid sporophytic phase.
• The plants are called algae which may be single celled (chlamydomonas), colonial (volvox) or filamentous( spirogyra)

BRYOPHYTA

• The plant body is thallus or foliose. Roots like rhizoids arise from underside to anchor the plant.
• These are simplest land plants, confined to damp places. These are also called AMPHIBIANS OF PLANT KINGDOM as they live on land but are dependent on water for sexual reproduction
• True vascular tissue is absent.
• Sex organs are multi cellular. Fertilization is external and they need water for gametes to move.Embryo stage is present .Sporophyte is dependent over the gametophyte stage.Sporophyte is differentiated into foot, seta and capsule.
• This division includes mosses and liverworts.( Funaria, Riccia, Marchantia)

PTERIDOPHYA

• The plant body is differentiated into true roots, stem and leaves.
• They are the highly evolved cryptogams.Stem is generally underground, leaves are made up of leaflets bearing sporangia on the underside.They are the first terrestrial plants to possess vascular tissues.
• These contain vascular tissue.
• Sex organs are multicellular and jacketed.Embryo stageis present. Main plant body is sporophye.
• This division includes ferns( Dryopteris, Pteris) and selaginella.

PLANT KINGDOM

PLANT KINGDOM

It includes all  the organisms with the following features:

1. Eukaryotic, multi cellular with photosynthetic mode of nutrition.These are normally called producers.
2. Body is usually branched and irregular. Growth in plants is unlimited .
3. Cell wall made of cellulose is present.
4. Food is stored in the form of starch.
5. The plants are usually fixed or free floating. Active locomotion is absent.
6. Asexual as well as sexual reproduction takes place. Embryo stage is present except in alga
7. Exceptions:
8. Cuscuta is a parasite.
9. Nepenthes , Drosera are insectivorous plants.

1. BASIS OF DIVISION OF KINGDOM PLANTAE

• Differentiation of plant body into distinct components.
• Presence of vascular tissue.
• Ability to bear seeds
• Enclosure of seeds in fruits.

SUBKINGDOMS:

Eichler divided the kingdom into two sub kingdoms

• CRYPTOGAMS: This group includes plants which are flowerless and do not bear seeds. In these plants, reproduction is carried on by some method other than the seeds or flowers. The sex organs are hidden and not conspicuous.
• PHANEROGAMS: This is the highest evolved group of plants. It includes flowering and seed bearing plants. They reproduce sexually by means of seeds.

DIAGRAMS OF MONERA

TYPICAL BACTERIAL CELL 

http://fyeahmedlab.tumblr.com/post/13342786720/diagram-of-a-bacterium

NOSTOC

ANABAENA

MYCOPLASMA

http://wallpaper222.com/explore/nostoc-diagram/http://www.gitam.edu/eresource/environmental/em_maruthi/mycoplasmas.htmhttp://www.dreamstime.com/stock-illustration-illustration-basic-shapes-bacteria-flat-design-image52338473

Features of monera ( diversity IX)

                                                           KINGDOM   MONERA
It includes all prokaryotic organisms chracterised by the following features:

1. These are basically unicellular and most primitive.
2. These are microscopic
3. Cell wall made of peptidoglycans or carbohydrates, proteins and lipids is generally present.( exception; mycoplasma ) They have a single membrane system.
4. All membrane bound organelles like mitochondia, lysosomes are absent.
5. Genetic material is not organized into nucleus.It consists of naked DNA (without histone proteins)and is called nucleoid.
6. They have various mode of nutrition i.e. saprobic, photosynthetic, parasitic, symbiotic, chemoautotrophic etc.
7. Bacterial flagella ,if present is simple and single stranded .
8. It includes all bacteria( E.coli), cyanobacteria (blue green alga i.e nostoc, anabaena) mycoplasmas.

HABITAT:These are the most abundant organisms on earth.They can live in extreme habitats such as hot springs, deserts, snow and deep oceans where very few other life forms can exist.
SHAPE: on the basis of shape bacteria can be grouped under four categories: spherical( coccus), rod shaped( bacillus), comma shaped (vibrio) and spiral (spirillum)
MODE OF NUTRITION: Some bacteria are photoautotrophic while others are chemoautotrophic i.e they oxidize various inorganic substances like nitrates, ammonia and use released energy for their ATP production.Most of them are heterotrophs i.e they do not synthesise their own food but depend on other organisms or on dead organic matter for food.
ARCHAEBACTERIA: These bacteria live in most harsh habitats . They differ from eubacteria in having a different cell wall structure which enables it to live in extreme conditions.
 Eg:  halophiles ( salty areas), thermoacidophiles(hot springs) and methanogens(marshy areas, gut of ruminants). Methanogens are responsible for production of biogas from the dung of these organisms.
REPRODUCTION:They mainly reproduce by fission. Under unfavorable circumstances they produce spores.
MYCOPLASMA: These are the smallest cells known and can survive without oxygen. These do not have a cell wall.They are pathogenic in plants and animals.

HIERARCHY OF CATEGORIES USED IN TAXONOMY

Linnaeus 's scheme of arranging organisms into an ascending series of groups of ever increasing inclusiveness is the hierarchial system of classification.

INCREASING SIMILARITY AS WE COME DOWN.

A category is known as taxon. The framework of taxonomic hierarchy is as shown . All the members of a taxon show similar characteristics which are different from that of the other taxa. As we go from species to kingdom, the number of similarities decrease.

SPECIES: It is the group of individuals with similar morphological characters, able to breed among themselves and produce fertile offspring. The members of species are structurally and functionally similar.

GENUS: It includes group of related species. They have identical reproductive organs, Eg Banyan and Fig have same kind of inflorescence, flower, fruit and seed and hence belong to a genus Ficus

FAMILY:it includes group of related genus. Eg: cats and lions belong to the same family Felidae as they have structure and claws.

ORDER: It is a group of families that resemble one another in few characters. Eg Tiger and wolf have jaws with powerful incisors and large sharp canines and are thereby placed in the order Carnivora.

CLASS: It includes organisms of related orders. Eg/; cats, dogs, bats, dolphins, kangaroos , monkey , camel are  in th class mammals due to hairy exoskeleton, milk glands etc.

PHYLUM: It includes organisms belonging to different classes having a few common characters. Eg : all animals which have a notochord present in the embryo are called chordates.

KINGDOM: It includes all organisms that share distinct common charaters. eg: Plantae.

System of classification ( diversity -2)

Artificial system of classification:
These system of classification were based on size, color or nature of the organism. It is helpful in quick identification of the organism.Aristotle classified the organisms on the basis of nature of their habitat ie terrestrial, aquatic or arboreal.Theophrastus classified known plants on the basis of their form, life span and habitat into four categories- trees, herbs and shrubs.The drawback of these system were that closely related organisms got separated into different groups while unrelated organisms got grouped together.

ARISTOTLE

THEOPHRASTUS

E.H.HAECKEL

WHITTAKER

Natural system of classification: These systems were based on natural relationship between different organisms and indicated similarities and differences between the organisms. 

Two kingdom classification: Traditionally all organisms were divided into two kingdoms: animalia and plantae. Shortcomings: Fungi are non motile but non photosynthetic. Some algae on the other hand were motile .Euglena and chlamydomonas has features of both plants and animals.

Three kingdom classification: E.H. Haeckel suggested a third kingdom protista to include unicellular eukaryotic microorganisms.

Four kingdom classification: Copeland introduced the kingdom Monera for all prokaryotic organisms.

Five kingdom classification: Robert H. Whittaker divided the organisms into five kingdoms namely: monera, protista, fungi, plantae and animalia.

Six kingdom classification: Woese further divided bacteria into Archaebacteria and Eubacteria on the basis of cell wall composition.

Diversity in living organisms (class 9 definitions )

Biodiversity , a concise form of biological diversity coined by Walter .G. Rosen refers to occurrence of diverse forms of living beings which differ from each other in external appearance, size, color pattern ,nutrition, behavior and habitat.

There is 1.7 - 1.8 million organisms on earth.

Taxonomy is a biological science which deals with identification, nomenclature and classification of organism following certain rules.

The vernacular names for one organism are different in different countries and not understood. So it is important to have a distinct, specific and universal scientific name.

Binomial nomenclature is the system of giving two names to one organism. The first is the name of the genus to which the organism belongs. It’s like our surname which we share with our family members.

The second name is species name that is possessed by only one kind of organism and it does not share it with any other organism in the genus.

The convention is that the genus name is written first with its initial letter in capital and species name is written after the genus name and its initial letter is always small.

Both are printed in Italics, and if handwritten both are underlined. Eg Rana tigrina

Both names are Latin names or have Latin endings.

This system of giving two names to an organism is known as binomial nomenclature and was developed by Linnaeus in his book Species Plantarium. So Linnaeus is also called Father of Taxonomy.

Classification is the method of arranging organisms into a hierarchy of closely related groups on the basis of similarities and differences.

Importance of classification:

1.       It makes the study of organism easy.

2.       It helps us to identify the organism.

3.       It gives relationship between two groups of organisms.

4.       It helps in finding complexity and evolution of various organisms.

BLOOD and LYMPH

Types of muscles and their differences.

http://www.majordifferences.com/2014/06/difference-betwee
http://www.majordifferences.com/2013/09/difference-between-cardiac-muscle-and.html#.Vdn37SWqqkon-striated-and-non.html

ELEMENTS OF XYLEM ( T.S) ( L.S.)

COURTESY GOOGLE IMAGES

Hormones

These are chemical messengers or information molecules which are produced by ductless glands and transported by circulatory system to other parts of body for inducing and coordinating their activities,

Characteristics:

1. These are produced by endocrine glands and poured into circulatory system
2. These act on specific cells , tissues and organs called target sites away from the place of origin.
3. Since these are transported by blood , their action is slow( except adrenaline)
4. These are small sized molecules of diverse origin-proteins, peptides, amino acid, steroids etc.
5. They are effective in very low concentration.
6. They are generally produced in response to a stimulus and are consumed during their activity in target cells.
7. Both their deficiency and excess is harmful.

Glands:

A cell, tissue or an organ that produces a secretion for performing a particular function is called gland. These can be 

1. Exocrine glands:These drain out their secretion through ducts into target sites which are adjacent to the gland. The secretion can be enzymes, mucus, excretory substances etc. Example:gastric glands, milk glands, sweat glands.
2. Endocrine glands: These are isolated glands which do not have ducts for draining out their secretion but put it into blood as their target sites are away from the point of origin.Their secretion comprises of hormones. Eg: Thyroid, pituitary gland.
3. Heterocrine glands: They have both exocrine and endocrine regions.Eg:Pancreas.

REFLEX ACTION

Spontaneous , involuntary and automatic response without the will of the organism.
The word reflex comes from refluxus which means reflected or directed back, which means that the reflex is reflected back from  the spinal cord.
Examples: coughing, sneezing, blinking of eye, salivation when food is eaten, sweating during exercise.
Reflex arc: The pathway taken by a stimulus to travel from receptor organ  to an effector organ.

Reflex arcs have evolved in higher animals for quick action in emergency situation when immediate action is needed for survival.
Reflexes can be put into two categories:

1. Unconditioned or simple or natural reflexes:These are inborn and inherited. Eg: blinking of eye, swallowing.
2. Conditioned or acquired reflexes.: one learns by experienceand gradually responds to it unconsciously.Eg. playing a musical instrument, working on keyboard of a computer,

Watering of mouth at the sight of food or closing of eyes when bright light id focussed on them is a cerebral reflex.
Importance:It checks overloading of the brain, provides immediate response to harmful stimuli and gives the organism a survival value.

BRAIN STRUCTURE

Human brain is the most advanced and well developed of all animals. It is encased in a bony case called cranium or skull which protects it from external injuries.
The brain is covered with meninges.Between the meninges , the space is filled with cerebrospinal fluids.
These are
DURAMATER -It is the outer tough and fibrous membrane.
ARACHNOID -It is  a middle delicate membrane.
PIAMATER- It is inner thin and highly vascular membrane.
ENCEPHALOGY is the  study of structure , working and function of brain.
The brain is differentiated into three parts:Fore brain,Mid brain and Hind brain.

FOREBRAIN:

1. Olfactory lobes
2. Cerebrum
3. Diencephalon

MIDBRAIN

1. Cerebral peduncles
2. Corpora quadrigemina

HIND BRAIN

1. Cerebellum
2. Pons
3. Medulla

CSF : It occurs between piamater and arachnoid and cavities of brain and sppinal cord.The fluid is rich in nutrients, hormones and respiratory gases.It supplies food , oxygen and removes wastes from brain, carries hormones from the brain and protects CNS from shocks. It is filtered from the blood and passes back into the blood

COMPONENTS OF NERVOUS SYSTEM X

                                           NERVOUS SYSTEM

1. CENTRAL NERVOUS SYSTEM  (CNS)
2. PERIPHERAL NERVOUS SYSTEM (PNS)
3. AUTONOMIC NERVOUS SYSTEM (ANS)

CNS

1. BRAIN 
2. SPINAL CORD

PNS

1. CRANIAL NERVES
2. SPINAL NERVES

ANS

1. SYMPATHETIC NERVOUS SYSTEM
2. PARASYMPATHETIC NERVOUS SYSTEM

NERVOUS SYSTEM

COORDINATION

It is the process through which two or more organs of an organism interact and complement the functions of each other or work together to adjust the vital activities of life.

NEED OF NERVOUS SYSTEM

1. To enable us to remeber, think and reason.
2. To coordinate working of various glands or tissues.
3. To regulate in voluntary activities of breathing , alimentary canal etc.
4. To regulate voluntary muscular activities.
5. To respond to changes in internal as well as external environment.

ROLE OF RECEPTORS

These are sensory cells that receive stimulus nad cinvert them into electric nerve impulses. The receptors are also called transducers as they convert one form of energy to another.
Examples

1. Photoreceptors in eyes
2. Phonoreceptors in internal ears
3. Olfactoreceptors in nose
4. Gustatoreceptors cin tongue
5. Mechanoreceptors in skin

INTRODUCTION TO CONTROL AND COORDINATION.

Stimulus
Any major or minor change in environment.

Receptor
Cell, tissue or organ sensitive to stimulus

In all animals control is achieved through

1. Neural System
2. Endocrine System

Difference between the two are as follows:

1. Nervous system is made up of nerve cells while endocrine system is made up of secretory cells.
2. Messages are transmitted in the form of electrical impulses in nervous control while these are transmitted as chemicals in hormonal control.
3. Impulses travel rapidly while hormone action is slow.
4. Effect of nerve impulse lasts for a short duration of time while effect of hormone lasts longer.
5. Impulses are transmitted along the nerve fibre while hormones are transmitted via bloo

CLASS IX FISH PRODUCTION

Fisheries can be categorised into two types.
1. Fin fisheries
2. Non-fin fisheries.
The fin fisheries of true fishes, whereas the non-fin fisheries is the fisheries of organisms other than true fish like prawn, crab, lobster, mussel, oyster, sea cucumbers, frog, sea weeds, etc.

Fin fisheries can be further categorised into two types
1. Capture fisheries
2. Culture fisheries.
Capture fisheries is exploitation of aquatic organisms without stocking the seed. Recruitment of the species occur naturally. This is carried out in the sea, rivers, reservoirs, etc. Fish yield decreases gradually in capture fisheries due to indescriminate catching of fish including brooders and juveniles. Overfishing destroys the fish stocks. Pollution and environmental factors influence the fish yield. The catches include both desirable and undesirable varieties.

Culture fisheries is the cultivation of selected fishes in confined areas with utmost care to get maximum yield. The seed is stocked, nursed and reared in confined waters, then the crop is harvested. Culture takes place in ponds, which are fertilized and supplementary feeds are provided to fish to get maximum yield. In order to overcome the problems found in capture fisheries to increase the production, considerable attention is being given to the culture fisheries.

Culture fisheries is conducted in freshwater, brackish water and sea waters. With the development and expansion of new culture systems, farming of a wide variety of aquatic organisms like prawns, crabs, molluscs, frogs, sea weeds, etc. have come under culture fisheries. Due to the culture of a variety of aquatic organisms, culture fisheries has been termed as aquaculture. http://agritech.tnau.ac.in/fishery/fish_classification.html

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