Biology Sem 1 : 2
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Kingdom Protista
Old group where all the “leftover” organisms were placed and Protista were a mix of living things that don’t fit into plants, animals, or fungi |
Q: Why don’t scientists use Kingdom Protista anymore?
Because the organisms in it are too different from each other — they don’t all belong in the same group.
What do all Protists have in common?
→ They are Eukaryotes — their cells have a nucleus.
→ They are either single-celled, or multi-celled without special body parts (like tissues).
How are Protists different from plants, fungi, and animals?
Protists don’t have special tissues, while the others do.
What kinds of bodies do Protists have?
They can be single-celled or multi-celled without special parts.
Are Protists one big family?
No — they are not one clade. They come from different family trees.
What does it mean that Protists are paraphyletic?
It means they don’t include all their relatives, like plants, fungi, and animals — they come from many lineages.
What is primary endosymbiosis?
It’s when a tiny plant-like bacteria (cyanobacterium) was swallowed by a simple eukaryotic cell, and they started living together. This made primary plastids.
What came from primary endosymbiosis?
Primary plastids — special parts in cells that help do photosynthesis, like in plants and algae.
What are the cell walls of these algae made of?
Cellulose, like in plants. This makes them different from other protists like Excavata or SAR.
What is Rhodophyta?
A group of red algae with about 10,000 species, mostly found in the ocean.
What color is Rhodophyta and why?
Red, because they have a pigment called phycobilins.
Does Rhodophyta have flagella (tails for swimming)?
No, they don’t have flagella at any stage.
Why is Rhodophyta important in the ocean?
They help build coral reefs and support marine life.
What is Chlorophyta?
A group of green algae with about 5,000 species, found in many places like oceans, lakes, and even on land.
How is Chlorophyta related to plants?
It’s closely related to land plants and has chlorophyll a and b, just like them.
What forms can Chlorophyta take?
They can be single-celled, colonies, or multicellular.
What is a key body feature of Excavata?
They have an asymmetrical body shape, which helps them move and eat in special ways.
What is the "excavated feeding groove"?
It’s a little groove on one side of the cell used to take in food.
How do Excavata move?
They use one or more flagella, which are like little tails that help them swim
What is special about their mitochondria?
Their mitochondria are modified or reduced, meaning they look and work differently than usual.
Do all Excavata use oxygen to live?
No — they have diverse metabolism. Some use oxygen (aerobic), others don’t (anaerobic).
How do Excavata live in the world?
Some are free-living, some live with other organisms (symbiotic), and some can be parasites.
What kind of body symmetry do Diplomonads have?
They have bilateral symmetry, meaning their body has two mirror-image sides.
How many nuclei do Diplomonads have?
They have two nuclei.
How do Diplomonads move?
They have many flagella — like little tails — to help them swim.
Do Diplomonads use oxygen?
No, they are mostly anaerobic, which means they live without oxygen.
What is special about their mitochondria?
Their mitochondria are reduced — they can’t make ATP, which is the cell’s energy.
How do Parabasalids move?
They move with flagella and an undulating membrane (makes wave-like motions).
What’s special about their mitochondria?
Their mitochondria are changed into hydrogenosomes, which make hydrogen gas (H₂) and work without oxygen.
What is Trichomonas vaginalis?
It’s a protozoan parasite that causes one of the most common sexually transmitted infections (STIs).
What does T. vaginalis look like?
It is pear-shaped, has 4 flagella, an undulating membrane, and one large nucleus.
Where does T. vaginalis live in humans?
It lives in the vagina (women) and urethra or prostate (men).
How is T. vaginalis spread?
Mostly through sexual contact. Rarely, it can be spread by wet towels or contaminated items.
Where do Euglenozoans mostly live?
In freshwater and marine environments.
Are Euglenozoans single or multi-celled?
They are single-celled.
What special structure helps Euglenozoans sense light?
They have a stigma (eyespot) and a photo-receptor to detect light and move toward it.
How do Euglenozoans get food?
They can switch between autotrophic (make their own food with light) and heterotrophic (eat other stuff) depending on the environment.
What are the 3 main types of body symmetry in living things?
Asymmetry – No symmetry; body can’t be split evenly.
Radial Symmetry – Body is like a circle; can be split into similar parts around a center.
Bilateral Symmetry – One straight line divides the body into mirror halves.
What is primary endosymbiosis?
Primary endosymbiosis is when a big cell (a primitive eukaryote) swallowed a smaller cell (a cyanobacterium) — but instead of digesting it, they worked together.
☀ The little cell became a plastid (like a chloroplast) that helps with photosynthesis.
What does SAR stand for, and what does it include?
SAR stands for Stramenopiles, Alveolates, and Rhizaria.
It’s a big group of eukaryotes that came from primary endosymbiosis and includes a mix of very different organisms.
What is secondary endosymbiosis?
It’s when a eukaryotic cell swallowed another eukaryote that already had a plastid.
This gave rise to new, more complex organisms like Stramenopiles.
What is special about Stramenopiles?
They usually have 2 flagella — one is hairy, and the other is smooth.
They include organisms like Diatoms, Brown Algae, and Water Moulds.
What are Diatoms and what are they made of?
Diatoms are unicellular algae with a glass-like shell made of silica.
They look like a shoe-box and are important for making oxygen in water.
What is Brown Algae and what gives it its color?
Brown Algae are multicellular marine algae with a brown color from fucoxanthin.
They include kelp forests, which are homes for many sea animals.
Are Water Moulds(Oomycetes) fungi?
No! They look like fungi, but their cell walls are made of cellulose, not chitin.
They are fungus-like, often parasitic or decomposers, and have lost their plastids.
What is the special feature of Alveolates?
Alveolates have alveoli, which are small, flattened sacs just under the cell membrane. This is their key feature.
What do Dinoflagellates look like and do?
Dinoflagellates are unicellular (2,000–2,500 species) with two flagella that move through grooves in their cellulose plates.
They can glow, cause red tides, and live in oceans.
What is the role of Dinoflagellates in coral?
Dinoflagellates live inside coral in a close partnership called a symbiosome.
They give the coral sugars from photosynthesis, and the coral gives them a home.
This partnership is very important for healthy coral reefs.
What makes Apicomplexans special?
picomplexans are parasites (5,000 species) that live inside other cells.
They have a special organelle called an apicoplast to help them enter and invade host cells.
What are the key features of Ciliates?
Ciliates (10,000 species) are heterotrophic protists that use cilia (tiny hair-like structures) to move, feed, and sense their surroundings.
They do not make their own food—they eat other things.
What is the key feature of Rhizarians?
Rhizarians are mostly unicellular protists that move and eat using thin, thread-like pseudopodia (tiny extensions of their body).
These help them crawl and capture food.
What are Forams known for?
Forams live mostly on the ocean floor (benthic) and have shells made of calcium carbonate.
They use pseudopodia to move and catch food.
What do Radiolarians look like and do?
Radiolarians are marine plankton with beautiful, silica-based skeletons.
They also use pseudopodia to catch food while floating in the ocean.
Unikonta
Traits:
Single flagellum
Actin filaments (movement, shape, division)
Monophyletic (one ancestor + all descendants)
Amoebozoans
Lobe- or tube-shaped pseudopodia
Mostly unicellular
Includes:
Slime molds (Mycetozoans)
Free-living amoebas (Tubulinids)
Parasitic amoebas (Entamoebas)
Slime Molds – Multicellularity Model
Single-celled → become slug when starved
Slug forms fruiting body
Model for how multicellularity evolved
Cellular Cooperation in Slime Molds
Some cells sacrifice themselves to form stalk (altruism)
Some try to cheat and become only spores
Shows tension between cooperation vs. selfish behavior
Slime Mold Communication
Use signal transduction to aggregate
Coordination → helps cells act like one organism
Helps us understand development & cell signaling
Genetic Studies with Slime Molds
Research on Dictyostelium
Insights into:
Cell division
Differentiation
Evolution of sex
Genes for multicellularity
Opisthokonts
Posterior flagellum
Heterotrophic:
Fungi = absorptive
Animals = ingestive
What is the key feature of Rhizarians?
Rhizarians are mostly unicellular protists that move and eat using thin, thread-like pseudopodia (tiny extensions of their body).
These help them crawl and capture food.
What are Forams known for?
Forams live mostly on the ocean floor (benthic) and have shells made of calcium carbonate.
They use pseudopodia to move and catch food.
What do Radiolarians look like and do?
Radiolarians are marine plankton with beautiful, silica-based skeletons.
They also use pseudopodia to catch food while floating in the ocean.
What is the special feature of Alveolates?
Alveolates have alveoli, which are small, flattened sacs just under the cell membrane. This is their key feature.
Alveolates have alveoli, which are small, flattened sacs just under the cell membrane. This is their key feature.
Dinoflagellates are unicellular (2,000–2,500 species) with two flagella that move through grooves in their cellulose plates.
They can glow, cause red tides, and live in oceans.
What is the role of Dinoflagellates in coral?
Dinoflagellates live inside coral in a close partnership called a symbiosome.
They give the coral sugars from photosynthesis, and the coral gives them a home.
This partnership is very important for healthy coral reefs.
What makes Apicomplexans special?
Apicomplexans are parasites (5,000 species) that live inside other cells.
They have a special organelle called an apicoplast to help them enter and invade host cells.
Examples include the parasite that causes malaria.
What are the key features of Ciliates?
Ciliates (10,000 species) are heterotrophic protists that use cilia (tiny hair-like structures) to move, feed, and sense their surroundings.
They do not make their own food—they eat other things.
What are choanoflagellates?
Tiny, single-celled creatures that are the closest relatives to animals.
Why are choanoflagellates important to science?
They help us understand how animals may have started long ago.
Can choanoflagellates form groups?
Yes, they can stick together to make small multicellular clusters.
What animal has cells that look like choanoflagellates?
Sponges—they have special cells called choanocytes (collar cells).
What do choanoflagellates and animals share in their DNA?
Genes for cell adhesion, cell signaling, and development.
What does "sister group" mean in this chapter?
It means choanoflagellates are the closest group to animals in the family tree.
What is ecology?
Ecology is the science that studies how living things (like animals and plants) and non-living things (like water and sunlight) affect where living things live and how many there are.
How is ecology different from environmentalism?
Ecology is science and uses data. Environmentalism is a social movement where people try to protect nature and reduce human damage to the Earth.
How is ecology different from natural history?
Ecology uses experiments and data. Natural history is more about observing and writing stories about nature — not much science.
What does the concept of multiple scales mean in ecology?
It means we can study nature up close (small scale) or from far away (big scale), and both ways give us important information.
What is a static scale in ecology?
A static scale is like a photo of nature — it shows what everything looks like at one moment in time.
What is a dynamic scale in ecology?
A dynamic scale is like a video — it shows how things in nature change over time.
How do static and dynamic scales work together?
The shape of nature (static) affects how animals live (dynamic), and animals also change the shape of nature over time.
What is a perturbation?
A perturbation is a disturbance or change in a system, like a storm or fire in an ecosystem.
What is perturbation amplification?
It's when a disturbance gets bigger and causes more problems.
What is perturbation damping?
its when a disturbance gets smaller and things go back to normal.
What are slow variables in ecology?
Slow variables change very slowly but affect big things over a long time (like climate).
What are fast variables in ecology?
Fast variables change quickly and cause short-term effects (like temperature or rainfall).
What happens if we keep changing fast variables over time?
Even small changes can pile up and start affecting the big, slow parts of nature.
Why is studying multiple scales important in ecology?
Because it helps us understand both the big picture and the tiny details of how nature works.
What is the second step in understanding where and how many organisms live?
It's looking at how physical variables like climate and geography affect living things.
Q: What are physical variables in ecology?
A: Things like temperature, rainfall, sunlight, and wind that come from nature and can’t be controlled by animals or plants.
Q: What is Earth’s climate?
A: It’s the usual pattern of weather in a place — like hot, cold, rainy, or dry — that happens over a long time.
Q: What are terrestrial biomes?
A: Big land areas with the same climate and types of living things — like deserts, forests, or grasslands.
Q: What is adiabatic expansion?
A: When air rises, it spreads out and cools down, which changes the temperature and can cause clouds or rain.
Q: What does adiabatic expansion do to the weather?
A: It helps make clouds and rain when warm air rises and cools.
Q: What is the Coriolis effect?
A: It’s how the spinning of the Earth makes wind and ocean currents curve instead of going in straight lines.
Q: Why is the Coriolis effect important in ecology?
A: It helps shape weather patterns and where rain or dry areas are, which affects where animals and plants can live.
Q: What is the Northern Hadley Cell?
A: It's a big loop of moving air in the Northern Hemisphere. Warm air near the equator rises, moves north, cools down, and then sinks — creating wind and weather patterns.