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2021-09-19 18:45:50 Human Evolution

Humans are evolved by gradual evolution
Human originated in east Africa
Human evolution started 15 mya

CHANGES OCCURRED IN HUMAN EVOLUTION
Left the arboreal life
Development of erect posture
Bipedal locomotion
Increase in the size of brain
Development of intelligence
Use of for limbs for on locomotory function

STAGES IN ORIGIN OF MAN
1. Apes
2. Ape man
3. Primitive man
4. Modern man


1. APES

15 mya, primates called dryopithecus and ramapithecus were existing

DRYOPITHECUS
Fossils of dryopithecus discovered by LSB Leaky in 1930
Dryopithecus is considered as ancestors of modern day apes
They had semi erect posture, thick hair, larger and sharper teeth and vegetarian
They were forest dwellers and spent most of time on trees

RAMAPITHECUS
Fossils discovered from shivalik hills in India
Rampithecus is considered as ancestors of man
They had man like dentition & spent most of time on land


2. APE MAN
This stage is intermediate between apes and men
Australopithecus was an ape-man because it combined may characters of ape and man
It is 2-5 million years old

AUSTRALOPITHECUS
It was discovered by Prof. Raywond Dart
Australopithecus probably lived in East African grasslands
They hunted with stone weapons but essentially ate fruit
They were 4 feet tall and weighed 60-80 pounds
It is considered as missing link between apes and man

3. PRIMITIVE MAN
Man originated about 5 mya
They are connecting link between australopthecus and modern man
Mostly lived in caves and used fire
They developed speech and buried dead bodies
Some important primitive men


i) HOMO HABILIS
First human like being
First known tool maker
They did not eat meat
Brain capacities were between 650-800cc
Fossils were discovered by Dr. Leakey from rocks in Africa

ii) HOMO ERECTUS
Homo erectus was the first true man
They had large brain with cranial cavity around 900CC
Many subspecies are discovered of Homo erectus as given below

a) JAVA MAN (HOMO ERECTUS ERECTUS)
Fossils was discovered in Java in 1891
They used fire for hunting, Protection and cooking
They used tools of bones and stones
Cranial capacity was 800-1000CC

b) PEAKING MAN (HOMO ERECTUS PEKINENSIS)
W.C. Pei discovered the fossils from china
Cranial capacity was 850-1300CC


4. MODERN MAN
Modern man include all the existing men and also some extinct men
They appeared 3 mya
Modern man originated in Asia around Caspian sea
Many subspecies are discovered of homo sapians

i) NEANDERTHAL MAN (HOMO SAPIENS NEANDERTHALENSIS)
They lived east and central Asia
Fossil was discovered by Fulhrott in Neanderthal valley of Germany
They has brain size of 1400CC
Developed speech

ii) CRO-MAGNON (HOMO SAPIENS FOSSILIS)
Cro-Magnon man was first extinct modern man
Fossils discovered by Mac Gregor from Cro-Magnon rocks of France
He become extinct 20000 Years ago
They had cranial capacity of 1650CC
They wore clothes of animal skin
Domestication was stared by this man
They also painted beautiful painting on cave walls

iii) MODERN MAN (HOMO SAPIENS SAPIENS)
Arose 75000-10000 years ago
This is the man of today having brain capacity of 1300-1600CC
This man has well developed chin, speech, smaller head and reduced body hair
Agriculture was started around 10000 Years back and human settlements stared Open / Comment

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2021-09-18 19:12:01 Theories of organic evolution

(i) Lamarckism: Lamarck (1744 –1829) was one of the most brilliant stars on the horizon of the history of evolution. He was the first naturalist to put forward a general theory of evolution in his famous book. Philosophic Zoologique published in 1809. His evolutionary theory may be summarised in the form of following laws:

(a) The internal forces of life tend to increase the size of an organism.

(b) The necessity in animals to produce new structures.

(c) The effect of use and disuse.

(d) Inheritance of acquired characters.

iii) Darwinism: Charles Robert Darwin was undoubtedly the first naturalist who put the idea of organic evolution on sound footing. His statements and theories were based upon practical experiences and large number of proofs which he collected directly from the nature.

His main ideas about the evolution are given below –

(a) Over – production of offspring

(b) Limited supply of food and shelter

(c) Struggle for existence:

(i) Intra –specific

(ii) Inter –specific

(iii) Environment

(d) Survival of the fittest

(e) Universal occurrence of variations

(f) Inheritance

(g) Natural selection Open / Comment

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2021-09-18 02:40:09 Menstrual Cycle

(1) Menstruation occurs in human, apes and old world monkeys.
(2) Menstruation is bleeding from the uterus of adult females at intervals of one lunar month.
(3) Beginning of menstruation or first menstruation is called menarche.
(4) The beginning of menstruation varies. It usually occurs between 12 and 15 years.
(5) The cycle of events starting from one menstruation till the next one is called Menstrual Cycle.
(6) In human females, menstruation is repeated at an average interval of about 28/29 days.
(7) One ovum is released (ovulation) during the middle of each menstrual cycle.
(8) It is regulated by certain hormones, some of which are secreted by the pituitary gland.
(9) The pituitary gland is stimulated by releasing factors produced in the hypothalamus.
(10) The hormones produced by the pituitary gland influence the ovaries. The hormones secreted by the ovaries affect the walls of the uterus.

Phases of Menstrual Cycle
The menstrual cycle consists of following four phases:

(1) Menstrual Phase:
(i) In a 28 days menstrual cycle,the menses takes place on cycle days 3-5.
(ii) The production of LH from the anterior lobe of the pituitary gland is reduced.
(iii) The withdrawal of this hormone causes degeneration of the corpus luteum and, therefore progestrone production is reduced.
(iv) Production of oestrogen is also reduced in this phase.
(v) The endometrium of uterus breaks down & menstruation begins.
(vi) The cells of endometrium secretions, blood & unfertilised ovum constitutes the menstrual flow.

(2) Follicular Phase:
(i) This phase usually includes cycle days 6-13 or 14 in a 28 days cycle.
(ii) The follicle stimulating hormone (FSH) secreted by the anterior lobe of the pituitary gland stimulates the ovarian follicle to secrete oestrogens.
(iii) Oestrogen stimulates the proliferation of the endometrium of the uterine wall.
(iv) The endometrium becomes thicker by rapid cell multiplication and this is accompanied by an increase in uterine glands & blood vessels.

Various Events during a Menstrual Cycle

(3) Ovulatory Phase:
(i) Both LH & FSH attain a peak level in the middle of cycle (about 14th day).
(ii) Oestrogen concentration in blood increases.
(iii) Rapid secretion of LH induces rupturing of graffian follicle and thereby the release of ovum.
(iv) In fact LH causes ovulation.

(4) Luteal Phase:
(i) Includes cycle days 15 to 28.
(ii) Corpus luteum secretes progestrone.
(iii) Endometrium thickens.
(iv) Uterine glands become secretory.

Hormonal Control of MC
(i) FSH stimulates the ovarian follicles to produce oestrogens.
(ii) LH stimulates corpus luteum to secrete progestrone.
(iii) Menstrual phase is caused by the increased production of oestrogens.
(iv) LH causes ovulation
(v) Proliferative phase is caused by the increased production of oestrogens.
(vi) Secretory phase is caused by increased production of progestrone. Open / Comment

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2021-09-17 12:15:40 Types of Teeth and Their Functions

There are 4 types of teeth in the oral cavity:

Incisors – The four front teeth in both the upper and lower jaws are called incisors.  Their primary function is to cut food.  The two incisors on either side of the midline are known as central incisors.  The two adjacent teeth to the central incisors are known as the lateral incisors.  Incisors have a single root and a sharp incisal edge.

Canines – There are four canines in the oral cavity. Two in the maxillary arch and two in the mandibular area.  They are behind and adjacent to the lateral incisors.  Their main function is to tear food.  They have a single, pointed cusp and a single root.  They have the longest root of any tooth.  They also serve to form the corners of the mouth.

Premolars (Bicuspids) – These teeth are located behind and adjacent to the canines and are designed to crush food.  There are eight premolars in the oral cavity.  There are two in each quadrant of the mouth.  The one closest to the midline is the first premolar and the one farthest from the midline is the second premolar.  These teeth can have 3-4 cusps.  The maxillary first premolar has two roots, and the remaining premolars have a single root.  There are no premolars in the primary dentition.

Molars – The most posterior teeth in the mouth are the molars.  They have broader and flatter surfaces with 4-5 cusps.  They are designed to grind food.  Mandibular molars typically have 2 roots.  Maxillary molars, which are located behind the second premolars, typically have 3 roots.  There are 12 molars in the permanent dentition with three in each quadrant of the mouth.  They are named starting with closest to the midline as first molars, second molars and third molars.  Although, some people do not fully develop the third molars.  Third molars are often referred to as wisdom teeth.  The primary dentition only contains eight molars.
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2021-09-16 20:26:33 Notes on Anatomy of Flowering Plants

Depending upon distribution of stomata, the leaves are :
(a) Apple-mulberry type: e.g. Oxalis, Mulberry, Apple.
(b) Potato type: e.g. Bifacial (dorsiventral leaves of pea, bean, tomato).
(c) Oat type: e.g. Suberect (isobillateral) leaves of most grasses and cereals (monocotyledens).
(d) Nymphea type: e.g. Floating leaves of Nelumbo, Nymphia, water lily.
(e) Potamogeton type: e.g. Submerged plants like Hydrilla, Vallisneria, Potamogeton.


(iv) Trichomes: These are epidermal outgrowths present temporarily or permanently on almost all plant parts.

(v) Root hairs: They are enlargements of special epiblema cells called trichoblasts and occurs in a particular zone of young root called root hair zone.

(2) Ground or Fundamental tissue system: Ground tissue system includes all the tissues of plant body except epidermal tissue system and vascular tissues. It forms the bulk of body. This tissue system mainly originates from ground meristem. The ground tissues constitute the following parts :

(i) Cortex: It lies between epidermis and the pericycle. The cortex is distinct in dicotyledons but not in monocotyledons where there is no clear demarcation between cortex and pith. It is further differentiated into :

(a) Hypodermis: It is collenchymatous in dicot stem and sclerenchymatous in monocot stem. It provides strength.

(b) General cortex: It consists of parenchymatous cells. Its main function is storage of food.

(c) Endodermis (Starch sheath): It is mostly single layered and is made up of parenchymatous barrel shaped compactly arranged cells.

(ii) Pericycle: It is a single layered or multilayered cylinder of thin-walled or thick-walled cells present between the endodermis and vascular tissues. In some cases, the pericycle is made up of many layers of sclerenchymatous cells (Cucurbita stem) or in the form of alternating bands of thin-walled and thick-walled cells (Sunflower stem).

(iii) Pith or Medulla: It occupies the central part in dicot stem, and monocot root. It is mostly made up of parenchymatous cells. in dicot root pith is completely obliterated by the metaxylem elements. In dicot stem the pith cells between the vascular bundles become radially elongated and known as primary medullary rays or pith rays.

(3) Vascular tissue system: The central cylinder of the shoot or root surrounded by cortex is called stele. The varying number of vascular bundles formed inside the stele constitute vascular tissue system. Xylem, phloem and cambium are the major parts of the vascular bundle. Vascular bundle may be of following types:

(i) Radial: The xylem and phloem strands alternate with each other separated by parenchymatous cells. such kinds of vascular bundles are called radial and found mainly in roots.

(ii) Conjoint: A vascular bundle having both xylem and phloem together, is called conjoint. Normally the xylem and phloem occur in the same radius. They occur in stems. Such vascular bundles are of two types:

(a) Collateral: A vascular bundle in which the phloem lies towards outerside and xylem towards inner side, is called collateral, e.g., Sunflower.

(b) Bicollateral: A vascular bundle having the phloem strands on both outer and inner side of xylem, is called bicollateral. e.g., Cucurbita. Open / Comment

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