This document provides an overview of the phylum Annelida, specifically focusing on the three main classes: Polychaeta, Oligochaeta, and Hirudinea. It describes the key characteristics of each class. Polychaeta, or bristle worms, are the most diverse group and can be errant or sedentary. Oligochaeta includes earthworms and freshwater worms. They lack parapodia and have few setae. Hirudinea are the leeches, which have suckers at both ends and a muscular system that allows inchworm-like movement. All classes reproduce sexually, though details vary between internal and external fertilization. In summary, the document outlines the defining features
In this Presentation, Phylum Ctentophora, Comb Jellies is described. After watching this you will learn the characteristics and examples of Phylum Ctentophora. The detail description of Pleurobranchia along with reproduction, colloblasts, mesoglea, comb rows and nerve net. It is part of BS Zoology Course Animal diversity.
Phylum Mollusca-my report..
sorry for some overlapping of texts... i was not able to edit it..it is actually because of the animations that i put it..... i just uploaded it directly :)
In this Presentation, Phylum Ctentophora, Comb Jellies is described. After watching this you will learn the characteristics and examples of Phylum Ctentophora. The detail description of Pleurobranchia along with reproduction, colloblasts, mesoglea, comb rows and nerve net. It is part of BS Zoology Course Animal diversity.
Phylum Mollusca-my report..
sorry for some overlapping of texts... i was not able to edit it..it is actually because of the animations that i put it..... i just uploaded it directly :)
Reptiles are a group (Reptilia) of tetrapod animals comprising today's turtles, ... The reptiles were, from the outset of classification, grouped with the amphibians. ... between lizards, birds, and their relatives on the one hand (Sauropsida)
This presentation provide information about salient feature of cyclostomata with proper examples and explanation why they are classified in this class.
It discusses basic information regarding a hemichordate animal called Balanoglossus or Acorn worm, which is also a good connecting link between the non-chordates and chordates.
There are main 5 classes of living echinoderms:
crinoids (sea lilies and feather stars); asteroids (STARFISH); ophiuroids (brittle stars); echinoids (SEA URCHINS, etc); and holothuroids (sea cucumbers).
Echinoderms have been well preserved as FOSSILS; all existing classes and several others now extinct were present in the Ordovician (505-438 million years ago). They may have originated in the Precambrian (over 570 million years ago).
Common name : sea lilies, Sea Stars(STARFISH), sea urchins, sea cucumbers, and brittle stars.
Habitat
Echinoderms occupy all habitats including coral reefs, mangroves, seagrass and soft-bottom areas.
Except for a few species which inhabit brackish waters, all echinoderms are benthic organisms found in marine environments. Echinoderms inhabit depths ranging from shallow waters at tide lines to the deep sea.(Barnes, 1987; Brusca and Brusca, 2003; University of Alabama Center for Communication and Educational Technology, 2000; Waggoner, 1999)
Habitat Regions
• temperate
• tropical
• polar
• saltwater or marine
Aquatic Biomes
• brackish water
Other Habitat Features
• intertidal or littoral
GeoGraphy and eco-system
Geographic Range
Mainly a marine group, echinoderms are found in all the oceans. (Brusca and Brusca, 2003)
BIOGEOGRAPHIC REGIONS
• arctic ocean
• indian ocean
• atlantic ocean
• pacific ocean
• mediterranean sea
Eco-system
Sea urchins are among the main herbivores on reefs and there is usually a fine balance between the urchins and the kelp and other algae on which they graze. A diminution of the numbers of predators (otters, lobsters and fish) can result in an increase in urchin numbers causing overgrazing of kelp forests with the result that an alga-denuded "urchin barren" forms.
Work cited:
Lawrence, J. M. (1975). "On the relationships between marine plants and sea urchins". Oceanographic Marine Biological Annual Review 13: 213–286.
Ecosystem Roles
Echinoderms are usually intricate parts of their ecosystems. Many asteroids are keystone species. Sea urchins, if not controlled by predators, may overgraze their habitat. Asteroids have several commensals, including polychaetes that feed on leftovers from the sea star's prey items. (Barnes, 1987; Brusca and Brusca, 2003)
Ecosystem Impact: keystone species
Cnidaria is a phylum containing over 9,000 species found only in aquatic and mostly marine environments. All cnidarians have radial symmetrical. There are two major body forms among the Cnidaria - the polyp and the medusa. Sea anemones and corals have the polyp form, while jellyfish are typical medusae.
Mollusca of India and need for conservationAshish sahu
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks. Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species
Reptiles are a group (Reptilia) of tetrapod animals comprising today's turtles, ... The reptiles were, from the outset of classification, grouped with the amphibians. ... between lizards, birds, and their relatives on the one hand (Sauropsida)
This presentation provide information about salient feature of cyclostomata with proper examples and explanation why they are classified in this class.
It discusses basic information regarding a hemichordate animal called Balanoglossus or Acorn worm, which is also a good connecting link between the non-chordates and chordates.
There are main 5 classes of living echinoderms:
crinoids (sea lilies and feather stars); asteroids (STARFISH); ophiuroids (brittle stars); echinoids (SEA URCHINS, etc); and holothuroids (sea cucumbers).
Echinoderms have been well preserved as FOSSILS; all existing classes and several others now extinct were present in the Ordovician (505-438 million years ago). They may have originated in the Precambrian (over 570 million years ago).
Common name : sea lilies, Sea Stars(STARFISH), sea urchins, sea cucumbers, and brittle stars.
Habitat
Echinoderms occupy all habitats including coral reefs, mangroves, seagrass and soft-bottom areas.
Except for a few species which inhabit brackish waters, all echinoderms are benthic organisms found in marine environments. Echinoderms inhabit depths ranging from shallow waters at tide lines to the deep sea.(Barnes, 1987; Brusca and Brusca, 2003; University of Alabama Center for Communication and Educational Technology, 2000; Waggoner, 1999)
Habitat Regions
• temperate
• tropical
• polar
• saltwater or marine
Aquatic Biomes
• brackish water
Other Habitat Features
• intertidal or littoral
GeoGraphy and eco-system
Geographic Range
Mainly a marine group, echinoderms are found in all the oceans. (Brusca and Brusca, 2003)
BIOGEOGRAPHIC REGIONS
• arctic ocean
• indian ocean
• atlantic ocean
• pacific ocean
• mediterranean sea
Eco-system
Sea urchins are among the main herbivores on reefs and there is usually a fine balance between the urchins and the kelp and other algae on which they graze. A diminution of the numbers of predators (otters, lobsters and fish) can result in an increase in urchin numbers causing overgrazing of kelp forests with the result that an alga-denuded "urchin barren" forms.
Work cited:
Lawrence, J. M. (1975). "On the relationships between marine plants and sea urchins". Oceanographic Marine Biological Annual Review 13: 213–286.
Ecosystem Roles
Echinoderms are usually intricate parts of their ecosystems. Many asteroids are keystone species. Sea urchins, if not controlled by predators, may overgraze their habitat. Asteroids have several commensals, including polychaetes that feed on leftovers from the sea star's prey items. (Barnes, 1987; Brusca and Brusca, 2003)
Ecosystem Impact: keystone species
Cnidaria is a phylum containing over 9,000 species found only in aquatic and mostly marine environments. All cnidarians have radial symmetrical. There are two major body forms among the Cnidaria - the polyp and the medusa. Sea anemones and corals have the polyp form, while jellyfish are typical medusae.
Mollusca of India and need for conservationAshish sahu
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks. Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species
Kingdom Animalia Phylum Chordata Class ReptaliaiPagador
In order for us to understand how all living organisms are related, they are arranged into different groups. The more features that a group of animals share, the more specific the group is. Animals are given scientific names so that people all around the world can communicate about animals, no matter what language they speak (these names are traditionally Latin words). Animals belong to a number of different groups, starting with the animal kingdom.
Kingdom
All living organisms are first placed into different kingdoms. There are five different kingdoms to classify life on Earth, which are Animals, Plants, Fungi, Bacteria, and Protists (single-celled organisms).
Phylum
The animal kingdom is divided into 40 smaller groups, known as phylum. Here, animals are grouped by their main features. Animals usually fall into one of five different phylum which are Cnidaria (invertebrates), Chordata (vertebrates), Arthropods, Molluscs and Echinoderms.
Class
The phylum group is then divided into even smaller groups, known as classes. The Chordata (vertebrates) phylum splits up into Mammalia (Mammals), Actinopterygii (Bony Fish), Chondrichthyes (Cartilaginous Fish) , Aves (Birds), Amphibia (Amphibians) and Reptilia (Reptiles).
Order
Each class is divided into small groups again, known as orders. The class Mammalia (Mammals), splits into different groups including Carnivora, Primate, Artiodactyla and Rodentia.
Family
In every order, there are different families of animals which all have very similar features. The Carnivora order breaks into families that include Felidae (Cats), Canidae (Dogs), Ursidae (Bears), and Mustelidae (Weasels).
Genus
Every animal family is then divided into small groups known as genus. Each genus contains animals that have very similar features and are closely related. For example, the Felidae (Cat) family contains genus including Felis (small Cats and domestic Cats), Panthera (Tigers, Leopards, Jaguars and Lions) and Puma (Panthers and Cougars).
Species
Each individual species within the genus is named after it's individual features and characteristics. The names of animals are in Latin so that they can be understood worldwide, and consist of two words. The first word in the name of an animal will be the genus, and the second name indicates the specific species.
Example 1 - Tiger
Kingdom: Animalia (Animal)
Phylum: Chordata (Vertebrate)
Class: Mammalia (Mammal)
Order: Carnivora (Carnivore)
Family: Felidae (Cat)
Genus: Panthera
Species: Panthera tigris (Tiger)
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
What is greenhouse gasses and how many gasses are there to affect the Earth.moosaasad1975
What are greenhouse gasses how they affect the earth and its environment what is the future of the environment and earth how the weather and the climate effects.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
2. Introduction
▪ Annelida is a group commonly referred to as
segmented worms, and they are found
worldwide from the deepest marine sediments
to the soils in our city parks and yards. Through
most of the 20th century Annelida was split into
three major groups; Polychaeta, Oligochaeta
(earthworms etc.) and Hirudinea (leeches).
3. ▪ Earthworms and leeches are the
familiar annelids for most people,
but polychaetes comprise the bulk
of the diversity of Annelida and
are found in nearly every marine
habitat, from intertidal algal mats
downwards.
4. There are even pelagic
polychaetes that swim or drift,
preying on other plankton, and a
few groups occurring in fresh
water and moist terrestrial
surroundings. Around 9000
species of polychaetes are
currently recognized with
several thousand more names in
synonymy, and the overall
systematics of the group
remains unstable (Rouse and
Pleijel, 2001).
Introduction
8. POLYCHAETA: Bristle Worms
▪ The vast majority of the more than 8,000 known species of
polychaete worms are marine; some, however, are found in
fresh or brackish water.They are abundant from the intertidal
zone to depths of over 16,405 ft (5,000 m).
The Sea Mouse The BomberWormsDiopatra
9. ▪ The polychaetes, so named
because of the numerous
setae (chaetae) they bear,
range in length from less
than 1/8 in. to more than 9 ft
(2 mm to 3 m), but most are
from 2 to 4 in. (5–10 cm)
long.Their colors are often
brilliant, and some species
are iridescent.The class has
usually been divided on the
basis of mode of existence
into two groups, the
errantia and the sedentaria.
CLASS POLYCHAETA: Bristle Worms
Fireworms, Eurythoe spp (A), C - Spirorbis,
'fanworm' or 'feather duster' worm (B)
10. Errant Polychaeta
▪ Errant polychaetes include
actively crawling or swimming
forms which may, however,
also spend time in burrows or
crevices, or under rocks on the
seashore. A familiar errant
polychaete is the
clamworm, Nereis, widely used
as bait.
11. Sedentary Polychaetes
▪ Sedentary polychaetes are
usually adapted to living
permanently in tubes or
burrows; some attach
themselves to rocks or
piers. Many sedentary
polychaetes, like the
lugworm, Arenicola, live in
burrows in sand or mud.
The majority, however, are
tube builders.
12. Polychaete
Anatomy
The structure of
the digestive tract
of polychaetes is
variable, reflecting
the diversity of
feeding types.
Respiration is
entirely through
the body wall in
some polychaetes,
and partially so in
most.
14. Above: a 3D model of a pair
of segments of a typical
errant polychaete, as viewed
from the anterior end.
Polychaete
Anatomy
15. ▪ The tentacles of feather-duster worms are used for respiratory
exchange as well as for feeding. A polychaete may have a
single pair of excretory tubes or a pair in each segment.
Sedentary polychaetes have various modifications to insure
that wastes will be deposited near the mouth of the tube or
burrow, where they are washed away.
Many species have thin-walled extensions of the body surface,
i.e., gills, used for gas exchange; most commonly the gills are
extensions of the parapodia.
Polychaete
Anatomy
16. POLYCHAETE REPRODUCTION
▪ Most polychaetes reproduce sexually, and the sexes are separate. Sex
cells develop from masses of tissue in the metameres and leave by
way of tubules or by rupture of the body wall. In most cases
fertilization of the eggs by sperm occurs externally in seawater and
results in the formation of free-swimming larvae.Variations include
internal fertilization, laying of egg masses that are attached to objects
with mucus, and brooding of developing eggs in the worm's body.
18. CLASS OLIGOCHAETA
▪ This class includes about 3,500 species of earthworms and
freshwater worms.The members of the class range in length
from about 1/32 in. to 10 ft (0.5 mm–3 m), but most are
comparable to the polychaetes in size. Oligochaetes occur in a
variety of habitats throughout the world. Most are burrowers in
the soil, but the class also includes worms that inhabit wells,
marshes, and swamps. Other species live under rocks on the
seashore, in the leaves of tropical trees and vines, on the surface
of glaciers, or on the gills of freshwater crayfish.
20. ▪ Like the polychaetes,
oligochaetes have bodies
divided into segments.
However, they lack
parapodia and, with a few
exceptions, have relatively
few and inconspicuous
setae.The setae are
usually arranged in four
bundles on each segment;
those of aquatic forms are
longer than those of land
forms.The setae of an
earthworm may be felt as a
roughness if one rubs a
finger along its side.
OLIGOCHAETA ANATOMY
22. ▪ Oligochaetes are less varied in their external form than the
polychaetes, but are much more numerous.
▪ As many as 4,000 oligochaetes have been counted in 1 square
meter of lake bottom, and about 9,000 in 1 square meter of
meadow soil.
▪ In almost all oligochaetes, the head is a simple cone-shaped
structure without sensory appendages.
▪ Light is detected by photoreceptor cells in the skin, usually
concentrated toward the front of the animal.
OLIGOCHAETA ANATOMY
23. OLIGOCHAETE DIGESTION
▪ The mouth, located under the head, leads to a relatively simple,
straight digestive tract consisting of a pharynx, an esophagus, and
an intestine, terminating in an anal opening.
24. ▪ Terrestrial oligochaetes tunnel through the ground, swallowing soil
as they go.The digestive tract of such a worm is specially modified
for this rough diet.Typically it has a thin-walled storage area, or
crop, and a muscular gizzard for grinding the soil to remove the
organic matter that is the actual food of the worm.
OLIGOCHAETE DIGESTION
25. OLIGOCHAETE CIRCULATION AND
RESPIRATION
▪ The circulatory system is that
typical of the annelids and has
many contractile vessels, or
hearts. Although a few aquatic
forms have gills for respiration,
most oligochaetes lack such
specialized structures and use
the capillaries of their body
walls for respiratory exchange.
Oxygen dissolved in the soil
water diffuses through the
moist epidermis of the worm.
26. ▪ Earthworms have a variety of sensory cells.Touch cells,
or mechanoreceptors, contain tactile hairs, which, when
stimulated, trigger a nerve impulse.The earthworm also has
light-sensitive cells. Such cells are more abundant in its
anterior and posterior segment, the parts of its body most
likely to be outside of the burrow. One of the earthworm's
most sensitive cells are those
that detect moisture.These
cells are located on the first
few segments.The animal also
appears to have taste cells. In
the laboratory, worms can be
shown to select celery in
preference to cabbage leaves.
OLIGOCHAETE NERVOUS SYSTEM
27. OLIGOCHAETE REPRODUCTION
All oligochaetes are
hermaphroditic, and nearly all
cross-fertilize by copulation.
Male and female reproductive
organs are located in separate
segments. The copulating pair
exchange sperm, which are
stored in the body of the
recipient worm until its eggs are
mature.
29. ▪ This class includes the 500 species of leeches,
flattened, predacious or parasitic annelids
equipped with suckers used for creeping.
Leeches range in length from about 1/2 in. to 8
in. (1 cm–20 cm); most are under 2 in. (5 cm)
long.They are commonly black, brown, green,
or red, and may have stripes or spots.
CLASS HIRUDINEA
30. ▪ Leeches are primarily freshwater annelids, but some live in the ocean
and some in moist soil or vegetation.The majority of leeches are
predators on small invertebrates; most swallow their prey whole, but
some suck the soft parts from their victims. Some leeches are
parasites rather than predators, and suck the body fluids of their
victims without killing them.The distinction is not sharp, as many
predatory leeches take blood meals on occasion.
31. HIRUDINEA
Distinguishing characteristics
▪ Distinguishing
characteristics -
Leeches have suckers at
both their oral and anal
ends (Fig. B).They are
usually flat so they
appear thin from the
side view (Fig. C).They
are relatively smooth,
lacking setae like other
annelids (Fig. D).
Leeches have variable
coloration, ranging from
light to dark, spotty to
striped (Fig. E).
34. HIRUDINEA
Reproduction
▪ Hermaphrodites, with
separate testis and
ovaries.The sexual
organs, and the ducts
that lead to and from
them are situated in the
anterior (front) part of the
animal, normally between
segments 7 and 15.
35. ▪ A courtship display is seen
among some leeches at the
time of mating.The fertilized
eggs are deposited in a
cocoon, secreted by the
clitellum; the cocoon is
buried in mud or affixed to
submerged objects.The
young emerge as small
copies of the adults.
HIRUDINEA
Reproduction Cont.