Green Valley College Foundation, Inc.
In-house LET Review
General Education:
General Science
JUSTINE N. KUSIN, LPT, MIB
LECTURER
HIERARCHY OF LIFE
Atom – The smallest unit of an element.
Molecule – A group of atoms bonded together.
Organelle – Specialized structures within a cell that
perform specific function.
Cell – The basic unit of life.
Tissue – A group of cells with similar structure and
function.
Organ – A group of different tissues to perform a
complex function.
System – A group of organs working together to
perform a complex function.
Organism – An individual living being.
HIERARCHY OF LIFE
ORGANELLE
MOLECULE
ATOM
Cell Biology
- Discovered the cell from the cork made from
the bark of oak tree (1665).
- He coined the cell (cellulae meaning a small
room) due to their resemblance to small
rooms or monk cells.
Robert Hooke
Cell Biology
Two types of cells: Eukaryotic Cells: Have a nucleus and membrane-
Prokaryotic Cells: Lack a nucleus and bound organelles (e.g., Plant, Animal cells,
membrane-bound organelles (e.g., bacteria Protists, and Fungi).
and archaebacteria).
Taxonomy
Taxonomy - The science of classification,
organizing, and naming living organisms based
on shared characteristics.
Carolous Linnaeus
(Carl Linnaeus, Carl von Linné)
- Father of taxonomy
- He introduce the Binomial Nomenclature.
Carolous Linnaeus
Levels of
Taxonomic
Classification
Three Domains of Life
Domain Archaea
Kingdom Archaebacteria
Single-celled microorganisms.
Extremophiles - hot springs, acidic
conditions, deep-sea hydrothermal
vents.
Initially considered bacteria but
were later recognized as a distinct
domain.
Domain Bacteria
Kingdom Eubacteria (Monera – old name)
Single-celled microorganisms.
Diverse in shape and size, including rod-
shaped, spherical, and spiral forms.
Lack a nucleus and membrane-bound
organelles.
Some bacteria are pathogens, causing
diseases, while others are beneficial, aiding
in processes such as nutrient cycling and
digestion.
Domain Eukarya
Cells with a true nucleus and
membrane-bound organelles.
Diverse in form and function, ranging
from single-celled organisms to
complex multicellular organisms.
Includes four kingdoms: Protista,
Fungi, Animalia, and Plantae.
Kingdom Protista
Mostly unicellular organisms.
Diverse group including algae, protozoa, and slime molds.
Kingdom Fungi
◦ Cell walls contain chitin.
◦ Heterotrophic, absorbing nutrients
via external digestion.
◦ Found in soil, decaying matter, and
symbiotic relationships.
◦ Play a crucial role in
decomposition, and nutrient
cycling.
Kingdom Animalia
◦ Multicellular organisms with
specialized cells, tissues, and organs.
◦ Heterotrophic
◦ Lack cell walls and have a complex
nervous system.
◦ It consists of two major groups:
Vertebrates and Invertebrates.
Phylum Porifera
Simple, asymmetrical or radially
symmetrical organisms.
Lack true tissues and organs.
Filter feeders, often sessile in
adulthood.
Example: Sponge (e.g., Grantia,
Spongilla).
Phylum Cnidaria
With tentacles containing
specialized stinging cells
(cnidocytes).
Two body forms: polyp and
medusa.
Example: Jellyfish, Coral, Hydra.
Phylum Platyhelminthes
Flat, unsegmented worms.
Bilaterally symmetrical with three
tissue layers.
Example: Planarians, Tapeworms,
Flukes.
Phylum Nematoda
Cylindrical, unsegmented worms.
Complete digestive system.
Example: Roundworms (e.g.,
Ascaris)
Phylum Annelida
Segmented worms with a true coelom.
Bilaterally symmetrical with distinct body
segments.
Example: Earthworms, Leeches, Polychaetes
Phylum Mollusca
Soft-bodied animals often protected by a
hard shell.
Muscular foot for locomotion.
Example: Snails, Clams, Squids, Octopuses.
Phylum Arthropoda
Segmented bodies with exoskeleton made
of chitin.
Jointed appendages.
Example: Insects (e.g., Honeybee,
Butterfly), Arachnids (e.g., Spider, Scorpion),
Crustaceans (e.g., Crab, Lobster).
Phylum Echinodermata
Radially symmetrical marine animals.
Endoskeleton of calcareous plates.
Example: Starfish, Sea Urchins, Sea
Cucumbers.
Phylum Chordata
Possess a notochord
Vertebrates (e.g., Fish, Amphibians,
Reptiles, Birds, Mammals).
Kingdom Plantae
Consists of multicellular organisms.
With a nucleus and membrane-bound
organelles.
Most plant cells have cell walls made of
cellulose.
Plants are autotrophic, producing their
own food through photosynthesis.
It has two types: Vascular and non-
vascular plants
Vascular Plants
Have specialized tissues for the transport of water, nutrients, and sugars.
Xylem: Conducts water and minerals from the roots to other parts of the plant.
Phloem: Transports sugars produced during photosynthesis from the leaves to other plant
tissues.
Examples: ferns, cone bearing plants (gymnosperms), and flowering plants (angiosperms).
Plant reproduction: sexual reproduction
Pollination
Cross pollination – From one plant to another plant.
Self-pollination – Pollination from the same flower.
Flower – Reproductive organ of flowering plants.
1. Sepals: These are the green leaf-like structures located at the base
of the flower. It is known as CALYX.
2. Petals: The colorful, petal-like structures of the flower that
surround the reproductive parts. It is known as COROLLA
3. Stamen: The male reproductive organ of the flower, consisting of
a filament (a slender stalk) and an anther (saclike container). The
anther produces pollen, which contains the male gametes (sperm).
4. Pistil (Carpel): The female reproductive organ of the flower. It
consists of the stigma, style, and ovary (it becomes the fruit). The
stigma receives pollen, and the ovary contains ovules (becomes
the seed).
5. Stigma: The tip of the pistil that receives pollen during
pollination.
6. Ovary: The lower part of the pistil that contains ovules (potential
seeds).
A complete flower contains sepals, petals, pistils, and stamens.
An incomplete flower is missing one of those parts.
Non-vascular Plants
Do not have specialized tissues for long-
distance transport.
Lack true roots, stems, and leaves.
Tend to be small and often found in moist
environments because they rely on water
for reproduction.
Examples: mosses, liverworts, hornworts
Homologous and analogous
structures
Homologous Structure
Are anatomical features that have a
similar evolutionary origin, indicating a
common ancestry.
They may have different functions in
different species.
Similarities are due to shared ancestry
and common developmental pathways.
Similar structures but serve different
functions in different organisms.
Homologous and analogous
structures
Analogous Structure
Are features that have similar function but
different evolutionary origins. Organisms
with analogous structures do not share a
recent common ancestor.
They may have different functions in
different species.
Similarities are due to shared ancestry.
Similar underlying structures but may serve
different functions in different organisms.
Ecology
Food Web
Trophic Levels
Fourth Trophic Level
Third Trophic Level
Second Trophic Level
First Trophic Level
Biological Interactions
Symbiosis
Mutualism: Both species benefit from the
relationship.
Example: Bees and flowers.
Commensalism: One species benefits, and
the other is neither helped nor harmed.
Example: Barnacles on a whale.
Predation: One species (predator) hunts
and consumes another (prey).
Example: Lions hunting zebras.
Competition: Different species compete for
the same resources, such as food or
territory. Parasitism: One species (parasite) benefits at
the expense of the other (host).
Example: Lions and hyenas competing
for a carcass. Example: Fleas on a dog.
Genetics
Gregor Mendel
was an Austrian scientist and Augustinian
friar who is often referred to as the "father
of modern genetics."
He conducted ground-breaking
experiments with pea plants in the mid-
19th century, providing the foundation for
our understanding of heredity.
Genetics
Phenotype – Observable traits of an organism (eye
color)
◦ Dominant gene (working gene) - An allele that is
expressed.
◦ Recessive gene (non-working gene) - An allele that is
masked by the dominant gene.
Genotype - The combination of alleles at a specific
gene locus (e.g., BB, Bb, bb for the gene
determining eye color).
◦ Homozygous - An individual having identical alleles for a
particular gene locus on both homologous
chromosomes.
◦ Heterozygous - An individual having different alleles for a
particular gene locus on homologous chromosomes
Biotechnology and
Bioremediation
Biotechnology
◦ Manipulation of an organism's genes to
introduce, modify, or delete specific traits.
◦ Modification of plant and animal genomes to
enhance traits.
Bioremediation
◦ Use of microorganisms to clean up pollutants
in the environment, such as oil spills, heavy
metals, and organic contaminants.
Green Valley College Foundation, Inc.
In-house LET Review
END OF SESSION 1
Biology
